The amount of Steem power you hold and Voting Power are the variables that determine how much your vote is worth since HF19. i.e. Voting power means the more you vote in a day the less your votes are worth until your voting power recharges.
Your vote will also be impacted by how many votes have been cast in the day by other voters on other posts and how much the price of Steem is.
According to Steemit FAQ
Hot - Popular posts at the moment.
Trending - Posts with the most amount of votes, stake-weighted, recently.
So hot posts are posts that are getting the most upvotes or comments, trending posts seem to be the same but stake weighted.
Got it. And reputation is how much other reputable users have upvoted you ever.