What does DIM do?

I keep reading near drastically different things from different websites about what it does    Some sites say they flush estrogen out of your system so you have more testosterone (sites trying to sell you their DIM supplements), other sites yell don't take DIM because it blocks testosterone (and then they sell you their supplements or body building program). And web MD just gives a kids level explanation that it reduces "bad" estrogen and raises "good" estrogen.