Snap Caps - Training Ammo

What are Snap Caps (Training Ammo) and how do you use them.

[@lilham10809]

thanks man, btw i subed your channel, hoping for more videos!

[@taco1030]

@shapesNforms i got some 30-30 ones for my marlin, i might buy some 22 magnum ones

[@lilham10809]

can you get them for .22 lr?