App is short for application, and it covers more than the icons on your phone. A native app is installed from an app store and runs on the device. A web app runs in the browser and needs no installation: Google Docs, Canva and most modern tools are web apps. A desktop app installs on your computer. Users increasingly cannot tell the difference, which is rather the point.
Why you keep hearing it
Because "I built an app" has become the signature sentence of the AI building boom, and it almost always means a web app. Tools like Lovable generate them from a description, and deployment services put them online in minutes. The phone app stores, with their reviews and waiting periods, are usually nowhere in the story.
What it means for you
Two things. First, when someone says AI built them an app in a weekend, picture a web page with working features, not something in the App Store. Second, and more useful: the word now includes things marketers can own. A campaign calculator, an internal brief generator, a quiz for a launch. Small, single-purpose apps have become something a marketing team can produce, not just request.