I infer that reputation (how much?) is earned for upvotes on posts (anywhere or just main?). I also know that there are no downvotes. What else affects reputation?
You earn stars when someone stars your question or answer.
* Initially, you can award one star to each post.
* When you reach a total star score of 10, you will be able to award one or two stars to each post.
* When you reach 100 stars, you can award up to three stars.
* ...and so on.
Questions can only be awarded stars if they are *meta* posts (all questions on meta, questions marked as local meta questions on main).
Your total stars are maintained separately on each site.