The higher your steem power, the more that your vote makes a difference by giving the author greater rewards. There's also voting power, which goes down every time you vote and slowly starts rebuilding to 100%, you can check your voting power at: https://steemd.com/@rishi556 . You can check how much your vote will be worth at : https://www.steemworld.org/@rishi556 . Just change the username after @ to your own.