Mobile application software runs on your phone or tablet and does a specific job
Mobile application software — usually called an app — is a program built to run on a smartphone or tablet. Unlike software that lives on your computer's desktop, an app is designed for a smaller screen, a touchscreen, and an operating system like iOS (Apple) or Android (Google). An app does one thing or a few related things: send messages, take photos, check the weather, play music, track your fitness, or manage your bank account.
The key difference between an app and a website is where it lives. A website runs in your browser and works the same way on any device. An app is installed directly on your phone and is built specifically for that phone's operating system. This means an app can use your phone's camera, microphone, location, and other hardware in ways a website cannot. It also means an app from Apple's App Store will not work on an Android phone, and vice versa.
Key Takeaways
- Mobile apps are programs installed on your phone or tablet that perform specific tasks, unlike websites that run in a browser.
- Apps are built for either iOS (iPhones and iPads) or Android (most other phones and tablets), and one version will not work on the other operating system.
- Apps can access your phone's hardware — camera, microphone, location, contacts — in ways websites cannot, which is why permission requests appear when you first open an app.
- Most apps are free or cost a few dollars, and you download them from the App Store (iOS) or Google Play Store (Android).
- Apps run faster than websites because they are stored on your device, though they take up storage space and need occasional updates.
How apps are built differently from websites
A website is written in code that any browser can read — Chrome, Safari, Firefox, Edge. The website lives on a company's server, and your phone downloads and displays it each time you visit. An app, by contrast, is written in a language specific to iOS or Android. The entire app is downloaded and installed on your phone, so it stays there even when you are not using it.
Because an app is already on your phone, it can start faster than a website. It can also work without an internet connection for some tasks — you can write an email offline in Gmail's app, for example, and it sends when you reconnect. A website usually needs a live connection to work at all. The tradeoff is that apps take up storage space on your phone, and they need updates from time to time as the company fixes bugs or adds features.
The two main operating systems and why they matter
Your phone runs either iOS or Android. iOS powers iPhones and iPads. Android powers most other phones — Samsung, Google Pixel, OnePlus, Motorola, and many others. Each operating system has its own app store: the App Store for iOS and Google Play Store for Android. An app built for iOS will not run on Android, and an app built for Android will not run on iOS.
This is why you sometimes see two download buttons on a company's website — one for iPhone and one for Android. The company has written the app twice, once for each system. Some small companies write for only one system, which means iPhone users cannot use their app at all. Most large companies, like Facebook, Instagram, and Spotify, maintain versions for both.
What permissions mean and why apps ask for them
When you open an app for the first time, it often asks permission to access your camera, microphone, location, contacts, or photos. These requests exist because apps can do things websites cannot — they can turn on your camera without you seeing it, record audio, or track where you are. Your phone's operating system requires the app to ask your permission first.
You can usually say yes or no to each permission. If you deny permission, the app may not work fully — a video calling app needs your camera and microphone, for example. You can change your mind later by going to your phone's settings and finding the app's permission list. Denying a permission does not break the app; it just prevents that specific feature from working.
Free apps, paid apps, and how they make money
Some apps cost money upfront — you pay a few dollars and download them once. Others are free but show advertisements. Still others are free but sell something inside the app — extra levels in a game, a premium subscription, or digital goods. A few apps are free with no ads and no in-app purchases, usually because a company built them to support a service you already pay for, like your bank's app.
When an app shows ads, the company makes money each time you see or click an ad. When an app has in-app purchases, the company makes money when you buy something inside the app. Free apps with ads or in-app purchases are the most common model because they let you try the app before spending money. You can usually uninstall an app and get a refund within a short window if you paid for it and changed your mind.
How apps use your phone's hardware and features
An app can access parts of your phone that a website cannot. A camera app uses your phone's camera. A fitness app uses your accelerometer — the sensor that detects motion — to count your steps. A maps app uses your GPS to know where you are. A messaging app uses your microphone to record voice notes. A photo editor uses your phone's processor to edit images quickly.
This hardware access is why apps can feel more powerful than websites. A web-based photo editor is slower because it has to send your photo to a server, edit it there, and send it back. A phone app can edit the photo right on your device. The tradeoff is that apps need permission to use these features, and they take up space on your phone.
Updates, storage, and keeping your apps running
Apps need updates. Companies release updates to fix bugs, add features, improve security, or make the app work with a new version of iOS or Android. Updates usually happen automatically if you have automatic updates turned on, though you can also update apps manually from the App Store or Google Play Store. Updates can be small (a few megabytes) or large (hundreds of megabytes), so they may take a while on a slow internet connection.
Apps take up storage space on your phone. A small app might use 50 megabytes. A large game might use several gigabytes. If your phone is running out of storage, uninstalling apps you do not use is one way to free up space. You can always reinstall an app later — your phone remembers which apps you have downloaded, and you can download them again without paying twice.
Frequently Asked Questions
Can I use the same app on my iPhone and Android phone?
No. An app built for iPhone will not work on Android, and vice versa. You would need to download the Android version from Google Play Store if you switch phones. Some companies maintain both versions, but not all. Check the app store for your new phone to see if the app you want is available.
What happens if I do not update an app?
The app will usually keep working, but it may become slower, less secure, or incompatible with your phone's operating system over time. Updates often fix security holes that hackers can exploit. It is a good idea to update apps regularly, though you can usually delay an update if you are busy.
Why does an app need access to my contacts or location?
An app needs these permissions to do its job. A messaging app needs your contacts to suggest people to message. A maps app needs your location to show where you are. A dating app needs location to find people near you. You can deny permission, but the app may not work as intended without it.
Can I use an app without an internet connection?
Some apps work offline — a notes app, a calculator, or a game stored entirely on your phone. Most apps need the internet for at least some features. A social media app needs the internet to load your feed, but you might be able to read posts you have already loaded. Check the app's description to see what it can do offline.
What is the difference between an app and a web app?
A web app is a website designed to look and work like an app on your phone. It runs in your browser, not as an installed program. Web apps are slower than native apps and cannot access your phone's hardware as easily, but they work on any phone without a separate download. Many companies offer both — a native app and a web version.