Not OP but…

The wiki is a vast resource on every little detail that’s being mapped. I find it a bit difficult to browse sometimes, easier to get to some pages via DDG, but this may just be me. The Beginner’s guide page I imagine might be a decent starting point.

Though I can’t say I myself started there… IMO the easiest way is to just get StreetComplete from F-Droid (or Google Play…), and wing it. That app is extremely user friendly, and literally just asks you a simple question about something in front of you, and as such allows you to fill in or verify some of the details on the map. It’s capable of a lot, but not quite everything, such as adding in new “ways” (roads, structures, anything not a single node).

When you’re not sure about something it’s asking, that’s when “winging it” should be replaced by “wikiing it”. Or looking it up any other way, since there are now decades of confused people asking questions online for your benefit!

Vespucci is the mobile app people tend to use for heavy duty editing, or just to do the stuff SC can’t. This one has a much scarier UI. It takes some getting used to and figuring out, but really isn’t so bad once you know how the app and OSM itself works. You can download it early on, but maybe just to appreciate how easy SC is, at first!

To answer your question about discussions: each “changeset” (SC manages these for you automatically, groups similar quests into the same changeset) can be commented on by any user if they noticed some issue in your edits, or want to ask for clarification. You can go to openstreetmap.org and click “History” up top to see recent changesets that affected the area within your screen. You’ll see that most won’t have a single comment, but if you’re logged in, you can see the option to start a discussion on any of them.