A handheld personal computer (PC), typically built around either a clamshell form factor or a gaming form factor with a gamepad integrated for video games, is a mobile device that is significantly smaller than any standard personal computer (PC), but based on the same principles as PCs. The clamshell form factor is sometimes referred to as a palmtop computer, not to be confused with Palmtop PC which was a name used mainly by Hewlett-Packard.

A mobile device or handheld computer is a computer small enough to hold and operate in the hand. Mobile devices are typically battery-powered and possess a flat-panel display and one or more built-in input devices, such as a touchscreen or keypad. Modern mobile devices often place emphasis on wireless networking, to both the Internet and to other devices in their vicinity, such as headsets or in-car entertainment systems, via Wi-Fi, Bluetooth, cellular networks, or near-field communication.