Blending of Animations/Sequences (player)

How does GMod smoothly blend the player animations, for example standing to walking and vice versa, as introduced in GMod 13? Function for blending sequences?
I can’t get it to work with ‘custom’ animations. Instead they very abruptly move from sequence to sequence because I can’t find a way to blend 2 sequences which GMod seems to do with the default player animations.

If I am correct, it uses gestures to do it.

Is everything a gesture?

I am not really sure, I think it’s only things like weapon hold types, and other misc animations like when a player talks on a mic. I may be wrong though.