The word "app" is an abbreviation for "application." It's a piece of software that comes pre-installed on your device, or it's software that you install on the device.

App is most often used in reference to a mobile app or a small piece of software that runs on a website. Another word for application is a program (although using the word program might make you sound dated).

Apps typically run locally on your device but can also run through a web browser. You can find apps on your computer, smartphone, tablet, or other electronic devices, including smart TVs and smartwatches. Apps may or may not have a connection to the internet.

There are three main types of apps:

Desktop apps: Built for computers with mouse and keyboard interactions.

Mobile apps: Designed for smartphones and touch inputs.

Web apps: Browser-based programs.

Desktop apps are usually much fuller than mobile apps and consist of all the app's features, whereas the mobile equivalent is a simpler and easier-to-use version.

This description makes sense when you consider that most desktop and web apps work best with a mouse, keyboard, and a large display, while mobile apps are accessible with a finger or stylus on a small screen.

Web apps might be full of features too, but they leverage the capabilities of an internet connection and web browser program. While some are heavy-duty and can perform well like mobile or desktop programs, most web apps are lightweight for a reason.

If an app is a mix between a web app and a desktop app, it might be called a hybrid app. These apps have an offline desktop interface, direct access to hardware and other connected devices, and an always-on connection to the internet for quick updates and access to internet resources.

Some apps exist in all three forms; they're available as mobile apps and desktop and web apps. Others work for mobile and web applications only.

The Adobe Photoshop image editor is an app that runs on your computer, but Adobe Photoshop Sketch is a mobile app that lets you draw and paint on a portable device. It's a condensed version of the desktop application. The same is true with the web app called Adobe Photoshop Express Editor.

Another example is Microsoft Word. It's available for computers in its most advanced form and on the web, by subscription, and via a mobile app.

While certain apps exist in all three app forms, that isn't always the case.

For example, you can get your Gmail messages through the official Gmail.com website and Gmail mobile app, but there isn't a desktop program from Google that lets you access your mail. In this case, Gmail is both a mobile and web app but not a desktop app. You can add it or remove it as desired.

Others (often games) are similar in that there are both mobile and web versions of the same game but maybe not a desktop app. Or, there might be a desktop version of the game, but it's not available on the web or as a mobile app.

Finding and acquiring apps differs based on the type of application.

In the context of mobile apps, almost every platform has a repository where users can download both free and paid apps. Mobile apps are normally accessible through the device or a website so that apps can be queued up for download the next time the user is on the device.

For example, the Google Play Store and Amazon Appstore are two places where Android users can download mobile apps. iPhone, iPod touch, and iPad devices can get apps through the iOS App Store straight from the device.

Desktop apps are more widely available from unofficial sources such as Softpedia and FileHippo.com. Official app repositories include the Mac App Store for macOS apps and the Windows Store for Windows apps.

Web apps load within a web browser and don't require downloading unless you're talking about something like Chrome Extensions. When you download them to your computer and enable them, the browser runs small web-based apps based on the feature.

Google refers to its online services as apps, but the company also sells a specific suite of services known as Google Workspace. Google has an application-hosting service called Google App Engine, which is a part of the Google Cloud Platform.