The numbers in brackets next to your name represent your reputation. It goes down if you get flagged, or downvoted by other individuals on the Steem system.

If you get upvoted, by those with a larger reputation, that number goes up.

Generally, if you aren't spammy; or abusive, your reputation will naturally increase.

Steem is a pretty complex blockchain, and the way Steemit represents the assorted bits and pieces is a bit overwhelming.

The best thing is to read the white/blue paper for Steem, which outlines how it's all meant to work. :)