Unfortunately you cannot see much of the CD-ROM inside the computer as the computer case is blocking the view.
The right image is what a CD-ROM looks like outside the cases
Click to enlarge the images.

What is it?

A CD-ROM is a drive when allows you to read CDs. It can read data CDs and it can also play music CDs. A data CD holds around 650MBs of information.

The Read-Only-Memory means that a CD cannot be written to or erased.

Most computer should have a CD-ROM nowadays.

Next : DVDs