Easy.

The key idea of the AppImage format is one app = one file. Every AppImage contains an app and all the files the app needs to run. In other words, each AppImage has no dependencies other than what is included in the targeted base operating system(s).

Trusted.

AppImage format is ideal for upstream packaging, which means that you get the software directly from the original author(s) without any intermediaries, exactly in the way the author(s) intended. And quickly.

Fast.

AppImages can be downloaded and run without installation or the need for root rights.