From ECDL.web

A touchpad (also trackpad) is a pointing device consisting of specialized surface that can translate the motion and position of a user's fingers to a relative position on screen. They are a common feature of laptop computers and also used as a substitute for a computer mouse where desk space is scarce. Touchpads vary in size but are rarely made larger than 40 square centimeters (6.3 × 6.3 cm or about 6 inch²).

As touchpads began to be introduced in laptops in the early 1990’s, there was often confusion as to what the product should be called. No consistent term was used, and references varied, such as: glidepoint, touch sensitive input device, touchpad, trackpad, and pointing device.

Touchpads are primarily used in self-contained portable laptop computers and do not require a flat surface near the machine. The touchpad is close to the keyboard, and only very short finger movements are required to move the cursor across the display screen; while advantageous, this also makes it possible for a user's thumb to move the mouse cursor accidentally while typing. Touchpad functionality is available for desktop computers in keyboards with built-in touchpads.

Apple's PowerBook 500 series was the first laptop to carry such a device, which Apple refers to as a "trackpad". When introduced in May 1994 it replaced the trackball of previous PowerBook models. Apple's more recent laptops feature trackpads that can sense up to five fingers simultaneously, providing more options for input, such as the ability to bring up the context menu by tapping two fingers. In late 2008 Apple's revisions of the MacBook and MacBook Pro have a different touchpad design with the button incorporated into the tracking surface.