Combo Drive
What are the difference between combo drive and Double-layer SuperDrive?
I presume you are reffering to macs here. The combo drive can read both CDs and DVDs but can only write CDs. The superdrive can read and write both CDs and DVDs.
personally given the large size of a lot of mac related stuff I wouldn’t buy a mac without a superdrive.
Flatmii Combo/Drive mode Installation Tutorial Part 1