Equalisation is known as EQ. It is a section on a mixer or in a software plugin that allows you to alter the frequencies of the sound on a channel. Typically, EQ can be:

• non-parametric - one control - boost or cut around a fixed frequency
• semi-parametric - two controls - select frequency and boost or cut around a fixed frequency
• fully parametric - three controls - select frequency, select width (how much around that frequency),  boost or cut around that frequency