typically in IT world, mouse pad is the square piece of plastic or rubber that you have under your mouse when you are using a desktop computer.
On a laptop the thing is called touchpad.
anyway, make sure that the touchpad is enabled, some laptops have a hotkey to turn it off. Also some laptops turn the touchpad off when you plug in an external mouse.
verify in device manager that synaptec pointing device is available on your computer and has the correct drivers installed.
if none of that helps you will have to explain what you've done before the touchpad stopped working