Equalization manipulates frequency in audio to either amplify frequency ranges or reduce them. Logic displays the frequency range and the volume of each so you can determine which parts are more impactful than others and edit accordingly. Knowing instrument frequency ranges and experimenting helps to understand what benefits from EQ and what could go wrong.
Above is a chart of what note in what octave is equivalent to what frequency.
Electric guitar could range from around 100Hz to 11,000Hz, so this range would be ideal to edit with EQ and anything below or above could be cut out to remove noise. Most other melodic instruments would fall within this range.