It has your account upvote posts super early, and when you're one of the first accounts to "discover" a post, you get a good reward (:

delegate me the sp :) ..i will tell you what it does ,,you can always undelegate at any time :P) ...if their bot is good you can earn tens if not hundreds of dollars per month
calculate:
they will auto-vote on your behalf till you reach 90% of voting power: that is approx. 10 votings per day
so by voting good contents across steemit meaning number of $ exceeds the number of voters amd with at least 10 votes per day and a curation reward of 0.1 minimum you gain:
10 x 0.1= 1 $
that in a month is 30$
...minimum
...the more sp you delegate the more money you gain
like with 10K you can make up to 600 $ per month
it all depends on how good are the bots in discovering great posts...in the end a great post is defined by the whales involvement or a post by a whale itself .. :) 
2 days ago I delegated 50 SP to @minnowbooster and gain every 24 hours about 0.04 on average so in another 12 hours I will be having a total of  0.12$ so in a month I will be having approx. 3.6 $
that is for only 50 sp
for 500 sp that is 10x times much or 36 $ which is approx the amount i calculated above

you can go to my wallet and check for the receivedSBD from minnowbooster and the time of transaction by hovering over the mouse on the date for the exact time which is every 2:23 am of eaxh day

this is my first delegation so hopefully it goes smooth or I will stop it at any time I wish..at the moment am letting it ferment..I want to wait for a month and see how much i gained and if it is worth it