It's a program that groups up people voting power and distributes it among the members. The more steem power you make up in the pool the more voting power you get from the pool. So as you are just starting out with a little steem power you will get a few up votes here and there a couple cents worth typically. As you grow in steem power as well in rank from time using shadowbot you will get more and more votes from the pool. The big thing is don't go spamming posts try to do one a day maybe two every now and then otherwise the bot will flag you as a spammer which doesn't help your rankings. There is a frequently asked questions page on the website I linked that goes into more detail.