What are mods and what the hell’s not?!?

I’ve been watching a lot of videos of RDR2, namely ones with sweet clips of Arthur taking out a whole house or area of baddies with style, stealth and finesse. Flipping around guns, diving and throwing multiple different knives and axes with flawless precision and fluid motion; extremely quick draws. It’s like re-enactments of Django.

The more comments I read on these vids, though, it seems nearly all these are mods.

Can someone help me differentiate what’s possible in the vanilla (console) game and what’s not??? I’ve been googling “advanced combat techniques RDR2” and nothing ever comes up.