Two quick world cup questions

[BeauJangles]

Why do the refs wear those mics? (or at least that's what it looks like they're wearing)

What language to the refs speak and how do the different languages affect the calling of the game and arguing calls and stuff?

 

[Mucho]

"The referee has an open mic, his two assistants and fourth
official can hear what is being said by him so they can have an insight
into the feel of the game.
"The referee can ask questions to his assistants with a push-to-talk mic
system that can be used to talk to the referee.
"It has lots of benefits - the most important being speed of
communication.

Text

AFIK sign language is often use