In electronics, bias usually refers to a fixed DC voltage or current applied to a terminal of an electronic component such as a diode, transistor or vacuum tube in a circuit in which AC signals are also present, in order to establish proper operating conditions for the component.
This issue is evident in HiFi or PA equipment. It is the same in an Overdrive or a Fuzz : even if their output signal is saturated, it has a specific shape that must not be damaged.
This article aims to take stock, being precise both from a technical point of view and from a musical point of view… It is a bit long, but I think it is useful.