A desktop computer is a personal computer in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Prior to the wide spread of microprocessors, a computer that could fit on a desk was considered remarkably small.
Desktop computers come in a variety of types ranging from large vertical tower cases to small form factor models that can be tucked behind an LCD monitor. “Desktop” can also indicate a horizontally-oriented computer case usually intended to have the display screen placed on top to save space on the desk top.
Most modern desktop computers have separate screens and keyboards. Tower cases are desktop cases in the earlier sense, though not in the latter. Cases intended for home theater PC systems are usually considered to be desktop cases in both senses, regardless of orientation and placement.
Desktops have the advantage over laptops that the spare parts and extensions tend to be standardized, resulting in lower prices and greater availability. For example, the form factor of the motherboard is standardized, like the ATX form factor.
Desktops have several standardized expansion slots, like Conventional PCI or PCI express, while laptops only tend to have one mini PCI slot and