When I move faces through each other, they automatically connect

[azzurrabluefox]

Hi! 

I most likely activated this option by accident but I really want to find its name because i find it kind of cool!

here's a gif of it in action

 

Does someone know what I did? 

thanks 🙂

[dmitriy.shpilevoy]

Isn't this how it works by default now? I think it's harder to disable it.