An application is a program you install on your phone, tablet, or computer that does a specific job

An application — usually called an app — is software designed to perform one task or a group of related tasks. Unlike your device's operating system (Windows, macOS, iOS, Android), which runs everything in the background, an application is something you open when you need it. You might open a weather app to check the forecast, a banking app to transfer money, or a photo editor to crop an image. Each application is built to solve a particular problem or let you do a particular thing.

Applications live on your device's storage — your hard drive, solid-state drive, or phone memory. When you tap or click the app's icon, your device loads it into active memory and runs it. The app stays open until you close it. Some applications run in the background even after you close them (like email apps checking for new messages), while others shut down completely.

The terms "application," "app," and "program" are used interchangeably in everyday language. On phones and tablets, people almost always say "app." On computers, people say "program" or "application" equally often. There is no technical difference that matters to you.

Key Takeaways

  • An application is a piece of software you install and open to do a specific task, separate from your device's operating system.
  • Applications are stored on your device and take up storage space, though you can remove them to free up room.
  • You download applications from official sources like the App Store, Google Play, or a software publisher's website.
  • Some applications run in the background after you close them, while others shut down completely.
  • Applications need permissions to access parts of your device like your camera, location, or contacts.

Where applications come from and how you get them

On iPhones and iPads, you download applications from the App Store. On Android phones and tablets, you use Google Play. On Windows computers, you can use the Microsoft Store, or download directly from a publisher's website. On Mac computers, you typically download from the App Store or directly from the publisher.

When you download an application, your device copies the software files to your storage. The download size varies widely — a simple note-taking app might be 5 megabytes, while a photo editing app or game can be 500 megabytes or more. Larger applications take longer to download and use more of your storage space.

Official app stores (Apple's App Store, Google Play, Microsoft Store) check applications before they appear, looking for malware and security problems. Downloading from these stores is safer than downloading from random websites. If you download an application directly from a publisher's website, make sure you are on the real website — scammers sometimes create fake download pages that look nearly identical to the real ones.

How applications use storage space on your device

Every application takes up space on your device. A small app might use 20 megabytes; a large one might use several gigabytes. Over time, as you install more applications, your device's storage fills up. When storage gets low, your device slows down because it has less room to work with temporary files.

You can see how much space each application uses. On iPhone, go to Settings > General > iPhone Storage. On Android, go to Settings > Apps > App Management, then tap each app to see its size. On Windows, go to Settings > System > Storage > Apps & features. On Mac, open Applications folder and right-click an app, then select Get Info.

If you need storage space, you can uninstall applications you no longer use. On phones and tablets, press and hold the app icon and select Remove or Uninstall. On computers, right-click the application and select Uninstall (Windows) or drag it to the Trash (Mac). Uninstalling removes the application and frees up the space it was using.

Permissions: what applications can access on your device

When you open an application for the first time, it often asks for permissions — access to parts of your device like your camera, microphone, location, contacts, or photo library. A weather app needs your location to show your local forecast. A video call app needs your camera and microphone. A photo app needs access to your photos.

You can grant or deny these permissions when the app asks. If you deny a permission, the app will still work, but it cannot use that feature. For example, if you deny a maps app access to your location, it can still show you maps — you just have to type in an address instead of getting directions from where you are.

You can change permissions later. On iPhone, go to Settings > Privacy and select the permission type (Camera, Microphone, Location, Photos). On Android, go to Settings > Apps > Permissions. On Windows and Mac, permissions work differently and are usually managed through system settings or the application's own settings menu. You can turn permissions on or off for each app individually.

Updates: keeping applications current and secure

Application developers release updates to fix bugs, add new features, and patch security problems. Updates are usually small — a few megabytes — and download automatically on most devices. On iPhones and iPads, go to the App Store, tap your profile icon, and scroll to see pending updates. On Android, open Google Play, tap your profile icon, and select Manage apps & device. On computers, most applications check for updates automatically or have an Updates menu inside the application itself.

You should install updates when they become available. Security updates fix vulnerabilities that hackers can exploit. Feature updates add new tools or improve how the app works. Updates rarely break anything, though occasionally a new version of an app works differently than the old one.

If an application stops working after an update, you can sometimes go back to the previous version by uninstalling and reinstalling it — though this is rare. More often, restarting your device or closing and reopening the app fixes the problem.

The difference between applications and web browsers

A web browser (Chrome, Safari, Firefox, Edge) is itself an application. But it is different from other applications because it displays websites instead of running its own code. When you open a browser and go to a website, you are not installing anything — you are viewing content that lives on a server somewhere else.

Some services exist both as applications and as websites. You can use Gmail as a website in your browser, or you can download the Gmail app. You can use Facebook in a browser or download the Facebook app. The app version is usually faster and can send you notifications, while the browser version works on any device without downloading anything.

Applications are generally faster than websites because they are already installed on your device. Websites have to download content every time you visit. Applications can also work offline (or partially offline), while websites usually need an internet connection.

Common problems with applications and how to fix them

If an application crashes or freezes, the quickest fix is to close it and open it again. On phones and tablets, swipe up from the bottom (iPhone) or tap the back button repeatedly (Android) to close the app. On computers, use Alt+F4 (Windows) or Command+Q (Mac) to force-close the application.

If an app keeps crashing, try restarting your device. This clears temporary files and memory, which often fixes the problem. If it still does not work, check whether an update is available — the crash might be a known bug that the developer has already fixed. If an update does not help, uninstall and reinstall the application.

If an application is running slowly, check how much storage space your device has left. If storage is below 10 percent, your device cannot work efficiently. Delete files, photos, or applications you do not need. You can also close other applications running in the background — on phones, swipe up or use the app switcher; on computers, look at the taskbar or menu bar to see what is open.

Frequently Asked Questions

What is the difference between an app and a program?

There is no technical difference. "App" is short for "application" and is used more often on phones and tablets. "Program" is used more often on computers. Both words mean the same thing: software you install to do a specific task.

Do I have to pay for applications?

No. Many applications are free and supported by ads or optional purchases inside the app. Some applications cost money upfront — you pay once when you download. Some use a subscription model where you pay monthly or yearly. The app store always shows the price before you download.

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

Sometimes. Some applications are available on multiple platforms — for example, Microsoft Word works on phones, tablets, and computers. Others are only available on one platform. Check the app store for your device to see whether the application you want is available.

What happens to my data if I uninstall an application?

It depends on the application. Some apps store data in the cloud (on a company's server), so your data stays safe if you uninstall and reinstall. Others store data only on your device, and uninstalling deletes that data. Before uninstalling an app with important data, check its settings to see whether it backs up to the cloud.

Why do applications ask for so many permissions?

Applications ask for permissions because they need access to parts of your device to work. A camera app needs camera access. A fitness app needs access to your motion data. You can deny any permission, though the app might not work as intended. Grant only the permissions the app actually needs to do its job.