what does the 440 hz thing mean that is on a guitar tuner? what does it do? how do you use it?
440 Hz is the frequency for A above middle C. It's the note you'll get on the 5th fret on your high E string. If you have an ear, you can tune your A string to the pitch 2 octaves below 440 Hz (110 Hz).
440 hz is concert pitch, its what most people tune to
Heh. Well...440 Hz is the note A. Concert pitch actually refers to the E-A-D-G-B-E tuning of a guitar.
440 is the amount of vibrations (per second I think) that an A above the middle C will make.