The computer case is the chassis containing the computer devices and power supply. Disk drive media refers to the things that you put inside of a disk drive to record data. Hard drives have magnetic metal oxides deposited on rigid metal disks for recording data. Floppy disks use a flexible vinyl surface covered in magnetic oxides. Disk drives are called non-volatile storage.
Information stored on a disk drive remains when the computer shuts down.
CD-ROMs record data by etching data onto vinyl disk media. A laser scans across the disk surface and produces reflections that are read by a detector. The power button turns on and off the computer. While some monitors get power by a plug on the back of a computer, most have their own plugs. Hard drive access is indicated by a LED next to the power and turbo LED's in most computers.