What are the things that musicians have in their ears when they perform?

Question

what does it help them with?

Answer 1

I think it helps them hear them selfs sing. Becuase they have to hear over the screaming croud and the instruments playing in the back round.

Answer 2

it is a small microphone to help them keep pitch and it helps them keep up with the music

Answer 3

It is a little microphone that helps them here how they sound when they are singing. I am a singer so I kinda have to know these things!