Answer:
A Hard Disk Drive is computer hardware that is used to read and write data onto the disk. It is mainly used for storing the PC's Operating System.
A CD is also a data storing device. It stands for "Compact Disk" meaning that it can store personal data such as pictures, movies, and other files. It is mainly used for Audio Recordings and Videos/Movies.
A Flash Drive (aka Thumb Drive), is a USB operated mini version of the Hard Disk Drive. It is also used for memory storage, and can be found in many different sizes. It is mainly used for pretty much every file you can find on a computer.
The term that describes these three devices would be
MEMORY