In Steem, the payout received for each article or comment is determined by the voting and flagging that takes place after it is posted. Your vote is a signal that you consider a post/comment should received a larger share of the reward pool than is currently pending. A flag, similarly, is a signal that you think it should receive a smaller share of the reward pool.
As you might expect, people vote more similarly to some people than others, and over a period of time we can analyse who we are voting most similarly too, and which accounts are flagging the content that we are voting for. We can say some accounts are voting cooperatively (or in synergy) with us, and some are voting competitively against our interests.
If you have at least 50SP, this tool allows you to see the high powered accounts who you are voting most similarly to, and who if anyone is voting against the things you are voting for. The time period covered is the previous 7 days.
The values are calculated as the sum of the products of SP weighted votes for each post where both accounts voted. This formula is quite likely to change as improvements come to mind.
EDIT: Thanks to 
