An insert point is a jack located on each channel that is usually used to take an effect and "insert" it into the signal path (compressors, reverb, what-have-you). On the Yamaha MG's, for example, the jack is located on the back of the mixer on each channel right above the inputs. Inserts are designed to be an input and output all in one--kinda like an effects loop but with one jack. If you want, you can use the inserts as "direct outs" by pushing a cable in there up to the first "click"...that way, only the output is activated. For some reason, this never shows up in the manuals, but it definitely works.