It does a lot of things really. The most useful feature is paid upvotes. For every 1 SBD you send you get about about $2.2 in upvotes, this is more than you paid and so you make a small profit. It helps you earn something for posting blogs and if you use the right tags can get you on the trending page for that tag for not much money so people actually read stuff you post.

Alternatively you could use it to sell your upvotes to get a small amount of SBD, you log in and authorise it and then they vote from your account and pay you some money in return. You can also lease SP so your upvotes are worth something but I'd just stick to the votes if you wanted to use it. Link: https://www.minnowbooster.com/vote-selling/?ref=525614