I have a mixer ( Yamaha n12 ). It has a high and low eq and also a mid with a separate q nob. In the manual it states the the high and low are shelving filters but explains no more than that. Would it be correct to assume then that the low would be a low shelf filter and the high be s high shelf the filter?
Yes, you are correct. Low filter shelves low frequencies and high shelve filter shelves high frequencies.
According to manual of your mix, low band is centered at 90Hz and high band is centered at 10kHz.