low gain boosts the set amount of Hz in the low range by dB.
Mid freq set frequency range
Mid gain boost the set amount of Hz in the mid range by dB.
High gain boost the set amount of Hz in the high range by dB.
In general Eq gains boost whatever amount of Hz was set, positive or negative meaning - or + dB. So Gain amplifies the amount of Hz that was set on the eq. You dont always have gain on an equalizer, you do have frequency bands or else it aint an equalizer hehe.
hehe...buy a cheap console, 16 chnls with british eq and sweeps ( second hand A&H mixwizard or a soundtracs )...and play with it...it's really all logical.