An Actor is anything that uses WorldEdit commands or certain APIs. Typically, an actor is a player, but they can also be a command block, the console, or perhaps an entity. As should be clear, an actor does not need a location in the world, although many actors also implement Locatable to provide this. A mod/plugin does not usually need to provide an actor to use the WorldEdit API, but actors may be provided in certain hooks such as EditSessionEvent (see Edit Session Event), allowing for customization based on who/what an actor is.