Bass and Treble are wider Low pass and High pass filters - the same as on some hi-fi equipment.
Bass is 0-100hz, treble is 10000hz+. These are standard ISO frequencies for bass/treble.
Bass and Treble are independent from Eq knobs, these are 2 extra bands. Also they can't/don't reduce level of their frequencies - 0% means no change of sound at all.