Zend certified PHP/Magento developer

Trouble understanding difference between disk and drives

So I’m studying for the A+ and we are currently learning about RAID configurations. It says Raid 0 requires 2 disk while Raid requires 2 drives. However wouldn’t Raid 0 still require two drives because each drive contain separate disk? Can you have two disk on one separate drive. Also what disk is used in SSD? Need help better understanding the difference between the two