Bit

A bit is the removable cutting tool chucked into a drill, router, or driver -- the general term covering everything from a twist drill to a Forstner bit, brad-point bit, or spade bit, each ground to a different tip geometry suited to a different kind of hole or cut. "Bit" and "cutter" are used close to interchangeably in casual shop talk, though "cutter" leans toward describing the actual cutting edge or profile shape, while "bit" more often refers to the whole tool.

A twist drill bit -- the plain, spiral-fluted, pointed bit sold in any hardware store -- is the default, general-purpose bit for drilling into wood, metal, or plastic; it doesn't leave as clean an entry hole as a brad-point or Forstner bit built specifically for wood, but it's the one bit type that works reasonably across every material a shop is likely to drill into.