A three letter acronym for "Hard Disk Drive". Frequently shortened to "Hard Drive". This is your computer's long term memory. Another analogy is a filing cabinet. The hard drive is the computer's filing cabinet. The RAM is your desk space. To perform work, you take papers from your filing cabinet and work on them on your desktop. This is the same as opening a file on the hard drive and working on it on your computer's "Windows desktop". Most of the "Microsoft Windows" naming conventions were based on a filing cabinet, desktop metaphor so users would feel familiar with the artificial computer interface.