Principles of Equalization

High Shelf	It cuts or boosts the frequency at the cutoff and all the frequencies higher than the set cutoff point. It has only two parameters: the cutoff frequency and the gain	It is usually used in the mid-high and high end of the spectrum. It can be effectively used to brighten up a track by using a positive gain of 3 or 4 dB and a cutoff frequency of 10 kHz and higher (be careful because this setting can increase the overall noisiness of the track). It can also be used to reduce the noise of a track by reducing by 3 or 4 dB frequencies around 15 kHz and higher
Low Shelf	It cuts or boosts the frequency at the cutoff and all the frequencies lower than the set cutoff point. It has only two parameters: the cutoff frequency and the gain	It is usually used in the low-mid and low range of the audible spectrum to reduce some of the rumble noise caused by microphone stands and other low end sources
High Pass	It cuts all the frequencies below the cutoff point. It has only one parameter which is the cutoff frequency.	It is a very drastic filter. It is often used to cut very low rumble noises below 60 Hz
Low Pass	It cuts all the frequencies above the cutoff point. It has only one parameter which is the cutoff frequency.	It is a very drastic filter. It is often used to cut very high hiss noises above 18 kHz. Use with caution in order to avoid cutting too much high end of the track.