In the gamemember

Now

The first tab: the next raid, what is waiting for you and what just happened in the guild.

In your game: Now

What it does: One column with three cards: Next Raid, with the countdown; Needs Me, with whatever is waiting for an action from you; and Activity, with the guild's last 48 hours. With a wide window, the next event with its reply buttons, your readiness, the guild pulse, recruitment, your loot and the guild chat appear beside it. Clicking a line opens the screen that handles it.
Who sees it: Everyone, and it cannot be turned off. Officers get more alerts in Needs Me.
Where to find it: Open the window with J or /gos: it is the first tab. It is also in the minimap button menu (right-click).

Next Raid shows the next Raid-type event in the calendar that has not started yet, with a countdown: 4:12:38 under a day, 2d 4h over a day.
Needs Me shows You haven't replied when the next calendar raid, within the next 7 days, still has no answer from you.
For officers, it also shows trials about to expire (in red, first), members inactive for more than 30 days, promotions to review and applicants waiting. At most 5 lines.
Activity covers the last 48 hours, newest on top, with up to 12 lines: who joined, left or changed rank, loot handed out, who leveled up and the raids logged.
The cards on the right only appear with a wide tab. In a narrow window, only the column remains.
While the tab is open, the countdown ticks every second and the lists refresh every 10 seconds.

Opened the window and did not land on Now? The window reopens on the last tab you used.
For a member, Needs Me almost always says All caught up: the other alerts are officer-only.
A raid scheduled on the site never shows up as unanswered: the reply is made through Discord or the site.
A guild join or leave can be missing from Activity. It comes from system messages, read by whoever has the addon and was online at the time.