That is called "reciprocal", it is a form of reflexive that indicates that an action perform by two parties falls on the other party reciprocally. Examples of this are:
Nos encontramos y nos abrazamos fuertemente.
We met (each other) and we hugged (each other) strongly
Por más que tratamos, no nos pudimos entender.
No matter how much we tried, we did not get to understand each other.
I hope this helps you.