Hi @orangina. Welcome to Steemit! :) Curation, to me, is anything you do to help support a blog post. So, yes, voting, comments and resteems. When I was new, I didn't have enough power to vote every post I visited, but I could still comment!

Curation is also grouping posts together, as you said, in an effort to share them with your audience and get more readers to quality content. There are other, more behind-the-scenes, curation efforts, like Curie, ocd, and other curation groups where people nominate posts. If they're approved, they get voted on by multiple players in a curation trail.

I don't know that much about curation trails because I haven't used them yet, but basically you sign up for an automatic vote that follows a leader. The lead account votes, and the trail votes behind them. You can set the % for your vote (once you have a slider), and in some autovote services you can also set it up so if your voting power (VP) drops below a certain point it lets you "rest" so your VP goes back up before you autovote again.

Lots to learn, eh? It's all good. Learn a little each day and have fun! Thanks for the comment. Hope that answered your questions. :)