Steem Dollars (SBD) accrues interest over time and over the course of a year will drastically increase.

Steem Power (SP) is what matters when you vote or comment on posts, including your own. The more SP you have the higher impact your vote has. Steemit calls this Vote Weight.
You can go to steemstats.com and add anyone in the box on the top left and it will show you tons of information that will help you figure this all out.