It means that a player has written something in the in-game chat.

You can open and close it with the tilde ' ~ ' key (under ' esc ', left from '1').

At british keyboards the key is ' ` '

At german keyboards the key is ' ^ '

At french keyboards the key is ' ² '

At spanish and latin american keyboards the key is ' | '

At arabic keyboards the key is ' ذ '

At scandinavian keyboards the key is ' § '

At russian keyboards the key is ' ё '

The key position is always the same.


PS: tell me when I wrote something wrong or when you have a country to add :D. I think it must be correct, thanks to Easter ChicagoTed7172 for english translating, thanks to Arielucho ama a Cinthia <3 for latinamerican addon, LogicFalls for british addon, 48du114h k455h4 for arabic addon, The Old Nite for scandinavian addon and Jack556 for russian addon.