Bandpass I've never heard of but bypass is usually the method by which an effects pedal turns itself off; usually heard in the context of "True bypass" which means that the signal actually takes a different physical path through the pedal when the effect is turn off which, in theory, means that your tone is coloured less by the pedal when it's turned off than it would be if it wasn't true bypass.
R.I.P. My Signature. Lost to us in the great Signature Massacre of 2014.

Quote by Master Foo
“A man who mistakes secrets for knowledge is like a man who, seeking light, hugs a candle so closely that he smothers it and burns his hand.”

bandpass is where it only allows certain frequencies through if im correct
GUITAR: Gibson Les Paul Special
AMP:Fender Vibro Champ XD