auto insert IS when you put in an autoboot cd and it boots up or runs a cd driven menu system or loads a game or loads up yer music player to play an audio cd !
its ok to leave it on on yer cd rom/dvd drive but advisable to turn it off on your Burner/Writer reason being if you read a disk to be burnt in your burner and it auto runs as soon as you close the cd door then it can be a pain in the backside with the program/game loading and running between disk insertions !!