Welcome to Steemit. I love photography so will be interested to see your posts. To be honest I am quite new myself, so I can't really go into details regarding the reward system. All I know is you build up reputation, you upvote posts and interact with people and you get rewarded for doing so. The little dollar sign I think is the value in money for the upvotes you have earned so far. The more upvotes the better! That is all from me. Most important is that this a positive and engaging community and we have to support each other. Good luck!