Hello, welcome to the F-Droid community. F-Droid is somewhere for FOSS meaning Free Open Source Software. As the name suggests, every app in this store is free and open source (you can see how the apps work and modify yourself). Another special thing of it is that the apps have no ads and trackers (unless some with the warning tags).
However, I don’t think it can be compared to Play Store as F-Droid wins in every aspect. For you, you are concerned on the ads which there aren’t here, but the more obvious and what we like here is that it the apps hosted here have no trackers.
You can check here for my article about it.
No it doesn’t. As far as I am concerned, F-Droid only works on donations and without ads because we care about privacy, not money!