Do you know anything about frequency range of hearing? Generally 20 cycles per second (Hertz) to 20,000 Hz. Low, low bass to very high frequencies we feel more than hear.
Vocals will be in the 1,000 to 4,000 range (men to women, in general). Instruments are also in fairly narrow sections of the audio spectrum.
https://en.wikipedia.org/wiki/Audio_frequency
https://en.wikipedia.org/wiki/Musical_acoustics
Basically you send a signal to the EQ that is not modified and the EQ will boost or cut a small section of that audio for each frequency section selected, center frequency of the adjustment listed as the control. Unlike a bass or treble control, these EQ controls make peaks and dips like a small mountain at each center frequency. Bass and treble generally boost/cut everything above(treble) or below(bass) a certain frequency in a ramp that has a max level, shelf. So you have a different way to change the sound of the signal. I would think the manual would have some really go information in it. Time to read it. Ask anything you want as you read through the manual, someone here knows the answer.