Graphic Equalisers offer a massive amount of control over any given sound source.
Unlike a semi-parametric EQ (usually found on mixing desks) that allows cut or boost of 2 or 3 frequencies, a Graphic EQ has a series of faders that represent the entire frequency range. Each one of these faders can be moved in order to boost or cut the volume of that particular frequency.
Separating & Editing Studio Music
Graphic EQs are particularly suited to instruments that cover the entire frequency range - for example, a vocal, drum kit room microphone, or an orchestra. Using a graphic equaliser, you're able to define the shape of the entire sound, rather than only fine-tuning a particular part of the sound.
They also come in handy for equalising your room - by putting a stereo graphic in front of your monitors, you can adjust any frequencies that are particularly loud or quiet in the room you use to mix in.