It isn't really a standard per say for laptops only, but the ones used in laptops are called half-height CDROM's. They are also quite often used in rack mount servers, dense blade servers, micro pc's, or any computer that needs to save space. If you're using a laptop like a Dell Latitude, the CDROM sits inside a special enclosure so that it'll fit in the Latitude drive bays. Other laptops with non-integrated CDROM's might also take this approach, but I'm not certain. I'm only familiar with Dell. For the integrated CDROM's, there is no enclosure, just the bare drive.
techfuzz