What is an app, and where should you get them?

A tool for one job

App is short for application: a program that does a particular job. Your phone's camera, calculator and messaging tools are apps. So are banking, maps, games and social media. On a computer, programs such as a web browser or a word processor are apps too.

If the operating system is the building, apps are the shops inside it. Each one has its own purpose, but they all rely on the building's power, doors and security.

Apps versus websites

Many services offer both an app and a website. The differences:

• Apps are installed on your device. They can work faster, send notifications, use the camera or location, and sometimes work offline.
• Websites open in a browser and need nothing installed. They take up no storage and are easy to use on any device.

Neither is automatically safer. Use whichever suits you, but always get the app from an official source and check you are on the real website.

Where to download apps safely

Use your device's official store: the App Store on iPhone and iPad, Google Play on most Android phones, and the Microsoft Store or the maker's own website on Windows. These stores check apps before listing them. Checks are not perfect, but they block a large amount of harmful software.

Be very careful with:

• Links in messages or adverts asking you to install an app, especially "to receive a parcel" or "to verify your account".
• Installing app files directly from websites (on Android, files ending .apk), unless you know exactly what you are doing.
• Apps with names very close to a well-known brand but a different developer name.

Check before you tap Install

• Developer name: is it the real company? Your bank's app should be published by your bank.
• Reviews and downloads: very few downloads for a "famous" app is a warning sign.
• Permissions: does a torch app really need your contacts and location? If the request does not fit the job, do not install.

Tip: You can change permissions later. On most phones go to Settings, then Apps or Privacy, and switch off anything an app does not need.

Keep your apps tidy

1. Turn on automatic app updates so security fixes arrive quickly.
2. Every few months, delete apps you have not used. Fewer apps means fewer things that can go wrong.
3. Review which apps can see your location, camera, microphone and photos.

Want the technical version? Our note on APIs explains how apps talk to online services.

Free apps and how they pay for themselves

Building and running an app costs money, so a free app usually earns it another way: adverts, in-app purchases, a paid upgrade, or collecting information about how people use it. None of these is automatically bad, but it helps to know which one applies. Read the short privacy summary in the app store, which lists the kinds of data the app collects and whether it is linked to you.

Watch for subscriptions that start after a "free trial". Set a reminder before the trial ends, and check your phone's subscriptions page (in the app store settings) to see what you are paying for each month. Cancelling there is usually quicker than looking inside the app itself.