what is the difference between TFT resistive touchscreen and TFT capacitive touchscreen?

TFT (Thin Film Transistor) is a type of display technology for LCD. It is not related to touch
screens in any way.
Resistive screens are an old technology, where there is a gap between two electrodes
in the screen and when you put light pressure there is a response as the electrodes
connect to register a touch at that point. They are cheap, but don't support multi touch
and reduce display quality by around 30% and require styluses. Resistive screens are uses in cheap touch screen phones, like the Nintendo DS among others.
Capacitive touchscreen is a new technology which also works on electrical conductivity,
but with the skin. Human skin conducts electricity lightly and capacitive touchscreens
discharge minute amounts of electricity and measure a touch response. They are more
expensive but support multi touch, are crystal clear and don't require styluses. However,
they can be triggered by mistake by metallic objects, cloth and other materials. They are used in the iPhone and most new smartphones including the Droid Incredible,
Blackberry Storm etc. The iPod trackwheel is also an example of this technology but
without the display