In the gamemember

Guild › Chat

Guild chat inside the window, with what was said while you were away.

In your game: Guild › Chat

What it does: Shows guild chat and lets you reply from there. In Forever the server keeps the history, so what was said while you were offline also shows up. Each guild channel you can read gets a tab: Guild, Officers and the ones the guild created.
Who sees it: Everyone. The Officers tab only appears for whoever the game lets read the officer channel.
Where to find it: In the window (J or /gos), Guild tab, Chat sub-tab. In Now, with a wide window, the same chat appears in the Guild chat card.

Each channel shows up to the last 200 lines.
Channel tabs only appear when there is more than one channel to choose from.
Your line appears when the game sends it back, not the instant you press Enter.
If you scrolled up, a new line does not pull the chat down. It only follows new lines when you are at the bottom.
Item and player links stay clickable, and a line break becomes a space.

During an encounter the game locks chat for addons: the message does not go out, the addon warns you and the text stays in the box so you can send it later.
While chat is locked, you cannot switch channels.