My 1996 Jeep Grand Cherokee Laredo just stopped starting. All lights, fan, sensors work but engine does nothing when I turn it to start position. What is wrong? Please help.

Assuming that when you turn your key the motor doesn't even try to start.
To start the combustion motor, an electrical motor is used to give it inertia, there are 2 possibilities: one, this electrical motor is not getting the electrical power required, or two, the electrical starter motor is broken. For the first option, check cables all the way from your battery, trough the switch you open or close with your keys, trough a capacitor, to the motor. This motor is generally below or next to the combustion motor, their shafts are mechanically connected by gears. Only the positive pole goes all this way, the negative terminal of the electrical motor is connected to your car's chassis, and so does the battery's negative terminal. If all these connections are OK, then your electrical motor is gone, in which case you'd better buy a new one and replace it, because fixing it would not be an easy task. You can try also replacing the capacitor, which must be on the way between the electrical motor and the key switch, if this is broken, your car should be very weakly trying to start as if the battery was low.