Coil tapping is when you take a lead out of the coil part way through the winding. The main result of this is that the sound cleans up slightly without losing too much volume, which makes it great for rhythm. You can only do this when winding the pickup.
When you take one coil of a humbucker it is commonly called coil tap, but it is actually shunting one of the coils to ground, so you have a single coil pickup, and should really be coil split.
Pinch harmonics are when you hit the string with the pick and the edge of your thumb, bringing out the octave of the note hit, because of the double hit.