Posted on 
Jan 29, 2006 10:35 pm cut is to reduce the output level of a frequency range. Like on a stereo receiver, or a radio, if you turn down the bass knob, this is 'cut'.
Boost is the opposite of cut, increasing output level of a certain frequency range.
Both of these terms are in relation to 0 db level. for example, if the signal coming from a CD player is coming in at a level of 80db, then lets say the bass and treble is coming in at 80db. If you let the bass go through your system and out to the speakers at a higher level, say 85db, then you've boosted. Conversely, if the bass is coming out your system speakers at 75db, then you've used 'cut'.
Rolloff is a ratio of EQ cut. The more in a frequency direction you go, the more cut is applied. So if you put a 100hz rolloff, then at 95hz there would be, maybe 1db cut. At 85hz, there would be 3db cut. At 75db there would be 6db cut, and so on, and so on. The EQ curve on the screen would go down, as the frequency goes lower.
Same as a high rolloff: the higher the frequency, the more the signal is cut.
There's also shelf EQ: at a certain frequency, all signal is cut totally. So say a 50hz high pass, or shelf, will only let signal above 50hz pass through. Anything under that will be removed.
Same as lo pass, say at 15khz, anything under can pass, anything over 15khz is removed entirely.
They're all useful in different situations, sometimes to remove rumble, or hum, lots of stuff.
Hope that helps.
