the @booster is an upvote bot,you pay them sbd or steem from your wallet along with your post link on which you would like to have an upvote, and the amount is distributed on percentage basis you simply have to go to https://steembottracker.com/bottracker.html and check a bot that best suits you(the one with max profit and refundable) and then go to wallet sbd and transfer to account with the postlink that's it.