What do they mean/do? Bass frequency? Low pass(something to that effect)? etc etc....anyone got a general overview?

 

those knobs are for cutting off frequencies to specific speakers and subs. as an example, if you have an amp to power a sub....you want to cut-off frequencies above 70hz. anything over 70hz would go to midrange and tweeters, any frequency below 70 would go to the subwoofer. low pass is used usually to send signals to a sub. high pass is for mid range and tweeters.