I’m fairly new here as well but here is my take on your two queries

1. You can send or “zap” sats from a connected lightning wallet to others if you like their content and vice versa. It’s not a requirement to use Nostr but it is part of the culture to get paid for your useful and helpful content or pay others for theirs. I can expand on this more but I’m not sure if you are a Bitcoiner so I don’t want to dump too much information on you.

2. Hashtags can help your posted notes get discovered when that specific hashtag is searched in the Universe screen. This is also not a requirement because your followers will still see your notes. But I do think hashtags are helpful early game for new users like you and I.