Quick meaning
Buying extra features, content, or premium access within a free app.
Think of it like this
Like entering a free exhibition but paying to see special exhibits inside.
Where you may see this
You may see this inside app stores, app settings, software updates, and install instructions.
Why it matters
Knowing the term helps you understand what an app is asking you to do before you tap, install, or change anything.
Say it simply
In-App Purchase means: Buying extra features, content, or premium access within a free app.