- Form factor (Form factor)
Internal drive is simply a drive, which is installed inside the casing of a computer, while an external drive has a casing of its own, and is connected to the computer via an cable. If you need to move the drive around a lot (e.g. use it in two or more different computers), an external drive is a practical choice.
- Connection type (Connection type)
An external Blu-ray-drive may be connected to the computer via an eSATA, FireWire, or USB interface, while an internal drive may be connected via IDE (ATA), SCSI, or S-ATA interface.
- Media load type (Media load type)
A slot load drive has an opening to slide the disc in (i.e. like many car CD players). In tray load drive the disk is placed on a tray that slides out of the drive.