EQ is short for equalization, which is the process of altering the levels of frequencies that comprise a signal. The three main frequencies that can be adjusted are bass, middle and treble.

On an amp, bass (or low end) is how many bass frequencies you want in the signal. The higher the bass, the fatter you sound!

Middle (or mid) is the middle frequencies of the signal. According to Kerry King of Slayer, middle gives your sound "balls" but this is completely a matter of opinion.

Treble (or high end) is how many of the higher frequencies you want in the signal. I like this fairly high because it makes it easier to pull off pinch harmonics, however too much can make your sound harsh and can result in unwanted feedback.

A very common effect on most guitar amps is reverb. Reverb is short for reverberation and makes you sound like you are playing in a large hall, where the sound waves would reflect off the walls and then into your ears. I generally like a subtle amount of reverb, however it depends on the song and the guitarist.

Fundamentally, drive (or gain) is how distorted your guitar sounds. Lower drive levels are nice for crunchy chords and higher drive levels are great for that heavy metal sound.

To see how artists such as Jimi Hendrix and Black Sabbath used EQ, click here.