With the hood up and standing in front of the car looking into the engine bay they are as follows.
Front right corner of the intake manifold-Temperature gauge sending unit-It will just have one wire connected to it
On the left side in the heater hard line, or directly into the intake manifold if some one removed the hard lines, is the ECT sensor (Engine Coolant Temperature) this will have 2 wire connected to it via a plug
On the #5 intake runner(first intake runner on the drivers front) is the ACT sensor (Air Charge Temperature) this sensor has 2 wires connected to it via a plug.
The ACT and the ECT provide feedback about the coolant temp and the incoming air charge temp to the ECU. The Temp gauge sending unit just runs the temp gauge in the instrument cluster.