A point in the signal path of a circuit where it is possible to interrupt the signal and “insert” another signal. Most commonly deployed in mixing boards it usually shows up as a patch point on each channel and/or bus output. The purpose is to be able to interrupt a signal in the mixer, bring it outside the mixer for some sort of special processing, and then return the processed signal to the same point from which it left. Common applications include applying compression, gating, or EQ to a particular channel without affecting any other channels or using any extra buses. Sometimes an insert is called a “patch” or “injection point.”