What does "app" mean?
You will learn what an app is in plain words.
An app is a small program on your phone or tablet.
Each app does one job. One shows the weather. One holds your photos.
The little squares on your phone screen are apps. You tap one to open it.
For example, the camera app lets you take pictures. That is an app.
Buddy says
You get new apps from the app store on your phone.