What is a Hard Drive?
A hard drive is a very crucial memory device, without it the computer cannot function. It is also known as a hard disk drive(HDD). When the computer needs them it reads them off the hard drive and uses them.
Types of Hard Drives
Modern hard drives come in two types, ATA and SCSI. ATA is the most commonly used format, as it is less expensive to produce. SCSI is used commonly in servers, as your can run more of them on one computer, they are faster and are often more durable.
How does a hard drive work?
In your computer's hard drive, there aren't really any iron nails. There's just a large shiny, circular "plate" of magnetic material called a platter, divided into billions of tiny areas. Each one of those areas can be independently magnetized (to store a 1) or (to store a 0). Magnetism is used in computer storage because it goes on storing information even when the power is switched off. In much the same way, the computerized information (or data) stored in your PC hard drive or iPod stays there even when you switch the power off.