Touch with one finger: Left mouse click.

Touch twice with one finger: Double mouse click.
Swipe with one finger: Move the cursor across the screen.
Left button: Left mouse click.
Right button: Right mouse click. (lower right zone of the touchpad)
Spread or pinch two fingers: Zoom in or out.
Swipe left or right with three fingers: Switch apps
Swipe up with three (or four) fingers: Multitasking view
Swipe down with three (or four) fingers: Show desktop

Swipe left or right with four fingers:

Switch desktops