There is not enough time or space to talk about every type of holster on the market. Holsters are like handguns: very personal, so you need to pick one that works for you. This little segment just talks very briefly about retention. Level 1 is nothing but friction. Level 2 includes a snap in addition to that friction. Level 3 is something you would see on a police holster—that is: friction, a snap or lever, AND a hood or other retention device.
Into the Fray, Episode 26: A Little Bit About Holsters | USCCA Video
Level 1 and beyond! Friction alone makes your holster a Level 1. Friction, plus a snap, makes it a Level 2. But there are more and different styles of retention. We cover them all in Concealed Carry Magazine.
For more great information, subscribe to Concealed Carry Magazine. We cover holsters all the time and regularly wade into the morass that is holster designation and proper use.