Glossary
Bundle identifier
An app's unique reverse-domain ID, such as com.apple.Safari, used to name the files it keeps.
What it is
Every Mac app declares a bundle identifier in its Info.plist. macOS uses it to name the app's container, preferences file and caches, for example ~/Library/Preferences/com.apple.Safari.plist.
Signed apps also carry a team identifier for their developer, and apps from the same developer can share a group container named with it.
Why it matters
Matching an app's leftover files by bundle ID and team ID, rather than by name, is what makes a complete uninstall safe.
In Activity Monitor
Not shown in the process list.
In iKnowMyMac
Each app's page lists every file it keeps. Remove completely matches them by bundle ID and team ID, and leaves files shared with other apps in place.
mdls -name kMDItemCFBundleIdentifier -r /Applications/Safari.appPrints an app's bundle identifier.
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