Refers to functions that happen either before (Pre Fade) or after (Post Fade) the main fader of a channel in a mixing board. For example, the Pre Fade Listen (PFL) is taken before (pre) the fader by definition. In certain situations it can be advantageous to monitor or take signals out of the board before or after the signal has passed through the fader. When driving headphone mixes or stage monitors, for example, it is common to use a pre fade aux send, so that the levels can be set independently of the fader position. It’s like having two separate mixes at the same time. Plus, you avoid unexpected levels being sent to the artists because you made a change for the main mix. On the other hand, it is customary to use a post fader signal to drive effects units such as reverbs, where it can be advantageous for mix of the signal sent to the reverb to be the same as the overall mix. Pull down a particular part in the main mix, and you also pull down its signal going to the reverb unit. Most of this is a matter of individual preference based on different circumstances. There are a number of other functions in a mixing board that may take place pre or post fade (inserts, EQ, dynamics, etc.) depending upon the board in question.