What is a level 3 holster?

What is a level III Duty Holster?
A level III Duty Holster refers to a three-point locking system with thumb-activated pivot guard. Here it mentions about levels of holsters. What are the levels of holsters? The primary characteristic that oftern distinguishes duty holsters from all other holster deisgns is retention. Law enforcement duty holsters are available with varying levels of rention security (i.e. Level I, Level II, Level III, etc...).  A level 3 holster has adjustable tension on the trigger guard, an auto lock that releases when the index finger is extended along the slide, and a pivot guard that releases when driving down on the holster with a master grip.
Gun&Flower Level III Glock 17 Duty Holster is a level III duty holster which has max comfort and security.