The first HDD was invented by IBM in 1956. They have fallen in cost and physical size over the years while dramatically increasing capacity. Hard disk drives have been the dominant device for secondary storage of data in general purpose computers since the early 1960s. They have maintained this position because advances in their areal recording density have kept pace with the requirements for secondary storage. Form factors have also evolved over time from large standalone boxes to today's desktop systems mainly with standardized 3.5-inch form factor drives, and mobile systems mainly using 2.5-inch drives. Today's HDDs operate on high-speed serial interfaces, i.e., Serial ATA (SATA) or Serial attached SCSI (SAS). 

The hard drive is sometimes referred to as the "C: drive" due to the fact that Microsoft Windows designates the "C" drive letter to the primary partition on the primary hard drive in a computer by default.

While this is not a technically correct term to use, it is still common. For example, some computers have multiple drive letters (i.e. C, D, E) representing areas across one or more hard drives.

You will often see hard drives advertised as being capable of a certain RPM (Revolutions Per Minute). This figure (as the name suggests) refers to how many times the spindle makes a complete 360º turn in any single minute.

The higher the RPM, the faster the data can be read from the platters, which increases overall performance.

RPM values range from about 5,400RPM to 12,000RPM and above.