In a nutshell, resistive, capacitive and I guess we could call it inductive.
A touch lamp dimmer operates very differently. Usually it detects the presence of AC from the 50/60 Hz power line that's ever present. Your body acts as an antenna.
Knobs and similar sensors can detect the change in capacitance when you touch them.
Touch screens can be resistive. There are resistors now which will change it's resistance depending on where you press. Resistive screens need to be calibrated.
Old technology that was used had a course X-Y matrix that was physically pressed made from a transparent oxide semiconductor like ZnO or ITO. There was also a technology that had IR detector and receiver pairs on the screen.
Here is a link to get started:
https://en.wikipedia.org/wiki/Touchscreen