F-Droid provides curated applications vetted by parties that *the user* chooses to trust.
By default, F-Droid provides only the applications that they themselves have verified and built from source. They also allow the user to add other sources from other parties who the user trusts (e.g. GuardianProject, IzzyOnDroid, and others[0]).
Google provides any application uploaded by any anonymous third-party who signs up as a developer (and in future, provides the required ID).