An equaliser divides sound into bands, from deep bass around 40 to 100 Hz, through the midrange where voices live (roughly 300 Hz to 3 kHz), up to the "air" above 10 kHz.
In mixing, EQ removes clashes, such as cutting a guitar’s low end so the bass is clear. When music plays under speech, a gentle dip in the midrange gives the voice room.
Using it in a prompt
Describe the result rather than settings: "dark and muffled" implies cut highs; "bright and crisp" implies boosted highs; "leave room for voice" implies a midrange dip.