The footprint
Each application is listed with the size of its bundle and everything it has put elsewhere: caches, containers, group containers, preferences, saved state, logs, login items and privileged helpers.
How a file is matched
On an exact bundle identifier, a dotted prefix of it, an exact folder name, or a group container prefixed with the developer’s team identifier. There is no substring matching, which is how an uninstaller takes a folder that was never the app’s.
The detail panel gives the reason each file was claimed, so you can disagree with it before anything moves.
Uninstalling
DiskDuo asks a running app to quit the way the Dock does, so it can offer to save first. Then the bundle and the leftovers you have ticked go to the Trash.
Trust
Each app shows how it is signed: by Apple, from the App Store, notarized, or signed by a developer without notarization — and anything unsigned, ad-hoc signed or changed since signing is called out.