An application program is software designed to perform a specific task for you

An application program — often called an app or application — is a piece of software built to do one job or a related set of jobs. Unlike the operating system that runs your device (Windows, macOS, iOS, Android), an application sits on top of that system and lets you accomplish something concrete: write a document, edit a photo, send an email, watch a video, or check your bank balance.

The key difference is purpose. Your operating system manages the hardware and keeps everything running. An application uses that operating system to let you work toward a goal. When you open Microsoft Word to write a letter, Word is the application. When you tap Instagram to share a photo, Instagram is the application. The operating system handles the background machinery that makes both possible.

Applications exist on every device: computers, phones, tablets, and even some smart home devices. They can be installed from an app store, downloaded from a website, or come pre-loaded on your device. Some are free, some cost money, and some work through a subscription.

Key Takeaways

  • An application program is software that performs a specific task, separate from the operating system that runs your device.
  • Applications range from productivity tools like word processors to entertainment apps like streaming services and games.
  • You install applications from app stores, websites, or they come pre-loaded, and they require an operating system to run.
  • Native applications are built for one operating system, while web applications run in a browser on any device.
  • Applications can be free, paid, or subscription-based, and they use your device's processing power and storage.

How applications differ from operating systems

The operating system is the foundation. It manages your device's hardware — the processor, memory, screen, keyboard, and storage — and handles tasks like file management, security, and running multiple programs at once. You do not directly use the operating system; you use what it provides.

An application is built on top of that foundation. It asks the operating system for permission to use the processor, access your files, display something on screen, or connect to the internet. The application does the specific work you want done, while the operating system handles the technical details underneath. Think of the operating system as the stage and the application as the performance on it.

This separation matters because it means you can replace applications without replacing your operating system. You can switch from Google Chrome to Firefox on Windows, or from Apple Mail to Gmail on a Mac. The operating system stays the same; only the application changes.

Types of applications and where they run

Native applications are built specifically for one operating system. Microsoft Word for Windows is different from Microsoft Word for Mac because each is written to work with that particular system. Native applications usually run faster and have access to more of your device's features, but you need a separate version for each operating system you use.

Web applications run inside a web browser — Chrome, Firefox, Safari, or Edge — on any device. Gmail, Google Docs, and Canva are web applications. You do not install them; you just visit the website and log in. They work the same way whether you are on Windows, Mac, iPhone, or Android because the browser handles the differences. The trade-off is that web applications sometimes run slower and depend on your internet connection.

Mobile applications are built for phones and tablets. You download them from the App Store (Apple), Google Play (Android), or other app stores. They are native applications designed for the smaller screen and touch interface of a phone. Some companies make both a mobile app and a web version of the same service.

What applications need to run

Every application needs an operating system to function. You cannot run Word without Windows or macOS. You cannot run an iPhone app on an Android phone. The application is written in code that the operating system knows how to execute.

Applications also need storage space. A small app like a calculator might use a few megabytes. A large app like Adobe Photoshop or a video game can use several gigabytes. When you install an application, it takes up space on your device's hard drive or solid-state drive.

Most applications also need processing power and memory (RAM). When you open an application, it loads into your device's memory so the processor can run it. If you open too many applications at once, your device slows down because it is dividing its processing power and memory among them all. Closing applications you are not using frees up that memory.

Many modern applications need an internet connection. Some require it constantly — streaming apps, email clients, and social media apps do not work offline. Others use the internet only for certain features; you can write in Google Docs offline, but you cannot save or share until you reconnect.

How you get and install applications

On phones and tablets, the easiest route is the app store built into your device. Apple devices have the App Store, Android devices have Google Play. You search for the app, tap "Get" or "Install", and it downloads and installs automatically. You need an account with the app store and, for paid apps, a payment method on file.

On computers, you have more options. Many applications are available through app stores — Microsoft Store on Windows, App Store on Mac — but you can also download installers directly from the developer's website. You download a file, run it, and follow the installation steps. Some applications also use package managers like Homebrew on Mac or Windows Package Manager on Windows, which handle downloading and installing from the command line.

Some applications come pre-loaded on your device. Windows computers come with Notepad, Calculator, and Microsoft Edge. iPhones come with Mail, Photos, and Safari. You can usually delete these if you do not want them, though some cannot be removed.

Free, paid, and subscription applications

Free applications cost nothing to download and use. Some are supported by ads — you see advertisements while using them. Others are made by companies that profit from other services; Google offers Gmail, Maps, and Photos for free because they collect data about your interests. Some developers simply choose to give their work away.

Paid applications cost money upfront. You pay once, usually between $0.99 and $50 depending on the application, and then own a license to use it. You do not pay again unless you buy a new version or upgrade. Many professional tools like Adobe Creative Suite or Microsoft Office used to work this way.

Subscription applications charge you monthly or yearly to use them. Microsoft Office 365, Adobe Creative Cloud, and many streaming services work on subscription. You pay regularly to keep access; if you stop paying, you lose the ability to use the application. Subscriptions are common for applications that need to update frequently or store your data in the cloud.

What happens when you use an application

When you open an application, the operating system loads it from storage into your device's memory. The application then displays its interface — the buttons, menus, text boxes, and other elements you see on screen. Everything you see and interact with is part of that application.

As you use the application, it processes your actions. When you type in a word processor, the application captures your keystrokes, displays them on screen, and stores them in memory. When you click a button, the application runs the code attached to that button. When you save a file, the application writes data to your device's storage.

Many applications also communicate with servers on the internet. When you send an email, your email application connects to your email provider's server and uploads the message. When you use a mapping app, it downloads map data from the provider's servers. This happens in the background while you use the application normally.

Frequently Asked Questions

What is the difference between an app and a program?

The terms are used interchangeably. "App" is shorter and more common on phones and tablets, while "program" is more common on computers. They mean the same thing: software designed to perform a specific task.

Can I use the same application on my phone and computer?

Sometimes. If the application is a web application, you can use it on any device with a browser. If it is a native application, you need a version built for each operating system. Many companies offer both — Spotify has apps for iPhone, Android, Windows, and Mac, but they are separate downloads.

What does it mean when an application crashes?

A crash happens when the application encounters an error it cannot recover from and closes unexpectedly. This can happen because of a bug in the code, a conflict with another application, or running out of memory. Restarting the application usually fixes it temporarily; updating the application often fixes it permanently.

Do I need to uninstall old applications before installing new ones?

No. You can have multiple versions of the same application installed, though usually only one is active. You can also have many different applications installed at once. The only reason to uninstall is to free up storage space or remove something you no longer use.

Why do applications ask for permission to access my camera or location?

The operating system requires applications to ask for permission before they can use sensitive features like your camera, microphone, location, or contacts. This is a security measure. You can grant or deny permission, and you can change your mind later in your device's settings.