In Fallout 4, there is a stat which counts the number of backstabs performed (at the bottom of the screen below). **What is a backstab and how do I perform one ?** 

[![enter image description here](https://i.stack.imgur.com/NLa2k.jpg)](https://i.stack.imgur.com/NLa2k.jpg)

I suppose it has to do with melee attacks and sneak, but I never found how to backstab someone...