PMOS
Beginner
The kind of transistor switch that turns on when its gate voltage is low. It is the mirror image of NMOS.
Novice
A p-channel MOSFET: p+ source and drain in an n-type well. It turns on when the gate is pulled sufficiently below the source, which usually sits at the supply voltage, so a low gate turns it on.
Expert
Hole channel with lower mobility, so it is made wider than the matching NMOS for equal drive. Passes a strong 1 and a degraded 0, so it forms the pull-up half of a CMOS gate.