An application is a program that runs on your device and does a specific job
An application (or app) is software designed to perform one task or a group of related tasks. Unlike your operating system — which manages your entire device — an application does something concrete: it lets you write a document, edit a photo, send a message, check your bank balance, or play a game. Applications run on top of your operating system and rely on it to function.
The word "application" is broad enough to cover everything from a simple calculator to complex software like Microsoft Word or Adobe Photoshop. On phones and tablets, people usually call them "apps". On computers, people often say "programs" or "software". They all mean the same thing: a tool you install and open to do work.
Applications are separate from each other. You can have dozens installed on your device without them interfering with one another. Each one has its own files, settings, and way of working. When you close an application, it stops running — though it stays on your device until you remove it.
Key Takeaways
- An application is a program that performs a specific task, like writing documents, editing photos, or managing email.
- Applications run on top of your operating system and need it to function, but they are separate from each other.
- You can install multiple applications on one device, and closing an application stops it from running but does not remove it.
- Applications come from different sources: app stores, websites, or physical media, and each source has different safety considerations.
- Uninstalling an application removes it from your device completely, though some files may remain in your system folders.
The difference between applications and your operating system
Your operating system (Windows, macOS, iOS, or Android) is the foundation that makes your device work. It manages your hardware — your screen, keyboard, storage, and memory — and handles basic tasks like turning on, shutting down, and connecting to the internet. You cannot remove your operating system without breaking your device.
Applications sit on top of this foundation. They ask your operating system for permission to use the screen, access your files, or connect to the internet. The operating system acts as a gatekeeper, deciding what each application can and cannot do. This separation protects you: a broken application does not crash your entire device, and a malicious application cannot easily access files it should not see.
Think of it this way: your operating system is the building, and applications are the rooms inside it. You can redecorate the rooms, add new ones, or remove ones you do not use. The building itself stays the same.
Where applications come from and how to install them
Most people install applications through an app store — the App Store on iPhones and iPads, Google Play on Android phones, or the Microsoft Store on Windows computers. These stores review applications before listing them, which reduces (but does not eliminate) the risk of installing something harmful. You search for the application you want, tap or click "Install" or "Get", and it downloads and installs automatically.
On Windows and Mac computers, you can also download applications directly from a company's website. You download a file, open it, and follow the installation steps. This method gives you more control but requires you to verify that you are downloading from the real website, not a fake one designed to trick you.
Some applications come on physical media like a CD or USB drive, though this is less common now. The installation process is the same: you insert the media, find the installer file, and run it.
Never install an application from a source you do not trust. Stick to official app stores and official company websites. If a website or email offers you a "free" version of paid software, it is almost certainly malicious.
How applications store their data and settings
When you use an application — changing settings, creating a document, or saving a photo — that data goes somewhere. Most applications store their files in a folder on your device that belongs to that application. On Windows, this is often in a folder called "AppData". On Mac, it is usually in "Library". On phones, the operating system hides these folders from you to keep things simple.
Some applications also store data in the cloud — on a company's servers on the internet. Gmail stores your emails in the cloud. Dropbox stores your files in the cloud. This means you can access your data from any device, but it also means your data leaves your device and is stored somewhere else.
When you uninstall an application, the program itself is removed, but some of its data files may remain on your device. This is usually harmless, but if you want a completely clean removal, you may need to manually delete these leftover folders. On Windows, some people use a "cleaner" application to do this automatically, though it is not necessary for most users.
Running multiple applications at the same time
Modern devices let you run many applications at once. On a computer, you might have your web browser, email, and a document open simultaneously. On a phone, you might have music playing in the background while you text someone. The operating system divides your device's processing power and memory among all the running applications.
Running too many applications at once slows your device down because it runs out of memory or processing power. If your device feels sluggish, closing applications you are not using will speed it up. On phones, closing an application is usually as simple as swiping it away. On computers, you click the X button or use Alt+Tab to switch between open applications and close the ones you do not need.
Some applications run in the background even when you are not actively using them. A messaging app might stay open to receive notifications. A music streaming app might continue playing. You can usually control which applications are allowed to run in the background through your device's settings.
Updating applications and why it matters
Application developers release updates to fix bugs, add new features, or patch security problems. When an update is available, your device usually notifies you or automatically downloads it. On phones, updates often happen automatically through the app store. On computers, you may see a notification asking you to restart the application to install the update.
Security updates are the most important kind. They fix vulnerabilities — weaknesses that hackers could exploit to access your device or steal your data. Ignoring security updates puts you at risk. If an application keeps asking you to update and you keep saying no, you are leaving a door open for trouble.
Feature updates add new capabilities or change how the application works. These are less urgent than security updates, but they are still worth installing because they often improve performance or fix annoying bugs. The only reason to delay a feature update is if you are in the middle of important work and cannot afford a restart.
Removing applications you no longer need
Uninstalling an application is straightforward. On phones, press and hold the application icon and select "Remove" or "Uninstall". On Windows, go to Settings > Apps > Apps & Features, find the application, and click "Uninstall". On Mac, open the Applications folder, find the application, and drag it to the Trash, then empty the Trash.
Some applications are harder to remove than others. On Windows, a few applications leave behind files or settings even after you uninstall them. On Mac, dragging an application to the Trash usually removes it completely. On phones, uninstalling is almost always complete.
If you are not sure whether you need an application, you can uninstall it and reinstall it later if you change your mind. Most applications are free to download again from the app store. The only exception is if you paid for the application — in that case, you usually do not have to pay again to reinstall it.
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 most often on phones and tablets. "Program" and "software" are older terms used more often on computers. They all mean the same thing: a tool that runs on your device to do a specific job.
Can I run the same application on my phone and my computer?
Sometimes, but not always. Some applications — like Gmail, Dropbox, or Microsoft Word — are available on both phones and computers. Others are made only for one type of device. Check the app store for your device to see if the application you want is available.
What happens if I close an application without saving my work?
Your unsaved work is lost. Most applications warn you before you close them if you have unsaved changes, but not all do. If you are working on something important, save it regularly. Some applications auto-save, which means they save your work automatically as you go.
Do I need to uninstall old applications to make room for new ones?
Not usually. Modern devices have enough storage for dozens of applications. However, if your device is running low on storage space, uninstalling applications you do not use will free up room. You can check how much storage you have left in your device settings.
Is it safe to download applications from the official app store?
App stores review applications before listing them, so the risk is lower than downloading from unknown websites. However, no review process is perfect. Stick to applications from well-known companies, read the reviews from other users, and check what permissions the application is asking for before you install it.