Q:

What is exactly a cross face position in BJJ? 

I'm training BJJ but my native language is not english.  I tried translation but it didn't work as well. 
So I'm wondering: what is a cross face?  I see people mentioning this cross face position, when passing the guard. 
I apreciate! 

A:

A crossface is a way to gain positional control of an opponent while working from side control (side control is also called cross side or side mount).  The gist of it is that you are driving shoulder pressure into the chin of your opponent to mitigate his/her mobility.  More specifically, using a crossface helps prevent your opponent from turning toward you so that they can either hip away from you or roll into you to initiate some sort of escape.  
Here is a good visual reference: 
https://www.youtube.com/watch?v=Y9DHk7DgL1w

