"handle" is the mother class of "event", "player", "widget", "force", "group", "trigger", "triggercondition", "triggeraction", "timer", "location", "region", "rect", "boolexpr", "sound", "unitpool", "itempool", "race", "alliancetype", "racepreference", "gamestate", "playerstate", "playergameresult", "unitstate", "aidifficulty", "eventid", "unittype", "gamespeed", "gamedifficulty", "gametype", "mapflag", "mapvisibility", "mapsetting", "mapdensity", "mapcontrol", "playerslotstate", "volumegroup", "camerafield", "camerasetup", "playercolor", "placement", "startlocprio", "raritycontrol", "blendmode", "texmapflags", "effect", "effecttype", "weathereffect", "terraindeformation", "fogstate", "fogmodifier", "dialog", "button", "quest", "questitem", "defeatcondition", "timerdialog", "leaderboard", "multiboard", "multiboarditem", "trackable", "gamecache", "version", "itemtype" and "texttag".
So, I suppose that you know exactly now, what a "handle" is. ^^