Where is the cooling fan sensor located?

Cooling fan not coming on. Can't find clear, concise, consistent information about the location of the correct sensor. People talk about vague engines, different names for the sensor and sometimes it's on the left, sometimes it's on the right and sometimes it's behind the engine. And most of the time I have no idea what any of these people are trying to describe.
A close-up line drawing is useless. My engine compartment looks nothing like a line drawing. Is there a difference between a cylinder head temperature sensor and an engine coolant temperature sensor? Do they both exit in the same car or only one? And which one controls the cooling fan? And how can I find it?
Engine: 3.0 L DOHC Duratec 30 V6.