Chillverse has two kinds of chat. Global Chat is one open conversation shared by everyone on Chillverse — it's always pinned to the top of your chat list and is a good place to meet other players. Direct messages (DMs) are private, one-on-one conversations between you and a specific player.
Since Global Chat is visible to the whole community, keep in mind that anything you post there is seen by anyone active in it — including staff who moderate the space. Direct messages are private between you and the other person, but standard chat rules still apply, and messages can be reported if someone breaks the rules.