Hi and welcome to Steem. Basically there is a certain reward pool each day that is distributed as rewards to the users. The way the rewards are distributed is based on voting. Since there are basically limited rewards, your voting power is also limited. Otherwise you could just keep posting comments and voting for yourself to shift the reward allocation towards yourself. So you have a certain 'voting power', which is a certain percentage. You can go to steemd.com/@c5cwf to see your current voting power. When you vote it depletes your voting power so that your votes become less valuable. Then over a certain number of hours your voting power builds back up again. I'm not sure if you see the slider bar when you vote, but if you do, adjusting the slider to a lower level will still apply one vote, but with less voting power behind it so it depletes your voting power less. I'm not sure how many votes it takes to fully deplete your voting power, but I would guess it is around 50(?) maybe. Realistically, you do not need to worry about this until you have higher Steem Power, and just focus on using the platform as you would any other social media. Upvote things you like, flag spam, etc... For users with low Steem Power, your best chance to earn rewards from the platform is by posting valuable content, and you're unlikely to receive much rewards from just voting. That doesn't mean don't vote though!

Best,
Trogdor