Most apps will be built using libraries to provide functionality.

For example a Lemmy might use a small database to store cached data on the device so it doesn’t have to redownload data as you navigate back and forth. Rather than writing their own code to create and maintain the database that functionality is available as a library they can import into their app and use immediately.

There might be dozens or even hundreds of libraries in any given app, this is great in that the app developer can focus on their app specific features and not worry so much about the low level features but these libraries also have their own release schedule and may only support security fixes on their current version.

This can result in a situation where you could have weekly or monthly updates just to include library updates even if you haven’t added any features directly to the app itself.