The touch pad replaces the mouse when the use thereof is not
possible, for example on a portable computer.
The touchpad works as a relative pointing device. There is
no relationship between the finger position and the cursor position on the
screen. However, some manufacturers make available API allows programmers to
know the absolute position of the finger and the pressure exerted.
The buttons on top or below the touch pad are used as mouse
buttons.
Some touchpads offer reserved areas can be used for
different functions, for example to scroll the scroll bars (like the wheel of a
mouse).
Synaptics touchpads (used with the correct driver) and keep
the party against the right edge of the pavement reserved for vertical
scrolling and the portion above the bottom edge reserved for horizontal
scrolling (even if no symbol in that did shown on your touchpad).
Some touchpads can emulate mouse click by tapping the
surface.
It is also possible to perform 3 clicks mouse buttons by
pressing the surface (eg with Linux and the Synaptics driver):
Left click → type with one finger;
middle-click → type with two fingers;
right click → tap with three fingers.
