I thought this week would be not informative. I thought I knew everything about EQ's. They make things sound better, right? Wrong!
Well, not only that. More than that, they are also used to cut frequencies. This is probably more important than boosting, because you have to make sure that all elements of your mix have room to live in. Making sure that everything mixes well, and isn't covering over anything else. This makes the EQ an integral part of the mixing process.