Issue:
Cursor is on screen but does it does not respond to you touching the touchpad.
Solution:
This is a fairly common issue and thankfully is quite easy to resolve.
Quite often this is is due to the touchpad being switched off by a function key. Finding the correct key on the F# keys can help (Lenovo V130 for example this is the F6 key).
Another way is to restart your system as the driver may have malfunctioned if the system has been on for an extended amount of time (typically over 3 or 4 days).
This should be sufficient for the system to reset the driver and get the touchpad working again.