I changed the video format to mpg, see if that works for you.
Yes, the follower is the piece of plastic at the top of the magazine spring. The "magazine insert" is the section of plastic that goes between the magazine spring and the floor plate.
Watch the video and let me know if you have any more questions. I think once you see that it will be clear.
CHP Training for VA, WV, NC, FL, TN, and others
HR218 / LEOSA Qualification Courses for VA LEO
NRA Law Enforcement Firearms Instructor / MTC / CRSO
GLOCK Firearms Instructor / G18 and Advanced Armorer
Defensive Training Concepts, Inc.