Lifters , the bit that follows the cam profile to move the push rod to lift the rocker up and down to open and close the valve
Buckets thats the bit over the top of the valve that holds in the springs and valve
Tappets or rockers are the bits that lift up and down via the pushrod as the lifter moves up and down via the cam profile

Do a google surely there would be a pic or two of a conbustion 4 stroke engine

Overhead cam engines well there different again .....