In the gamemember

Professions

Who in the guild makes what, and what nobody makes yet.

In your game: Professions

What it does: Lists the guild's professions with each one's recipes and who can make them. In Recipes you search for a recipe and filter by All, In guild or Nobody makes it; in Crafters you see who has the profession and at what level. Clicking a recipe opens a card with reagents, source and crafters, with Whisper for whoever is online.
Who sees it: Everyone. If the tab is turned off, the names of whoever makes the item still show in the tooltip.
Where to find it: In the window (J or /gos), Professions tab. The Find Crafter button is at the top of the tab. Switch it on and off in Settings › General › Modules; the tooltip, in Settings › General › General Options.

Your recipes are read without you opening the profession window. Opening the window only adds any recipe the addon does not know yet.
Each person's addon tells the guild what they know a few seconds after they enter the game, and then every 10 minutes.
Learned a recipe? It goes out to the guild about 10 seconds later.
In the list on the left, primary professions come first and secondary ones after, each group in alphabetical order.
The crafters column shows up to 3 names, online ones first, and +N for the rest. With nobody, it shows nobody in red.
In Crafters, whoever has the addon comes first, from highest level to lowest; whoever does not is at the end.
In an item's tooltip, Created by: lists who in the guild makes the item. With Only when holding Shift ticked, the line only appears while Shift is held.

Whoever does not have the addon shows up only with the profession name, with no level and no recipes, and never counts as someone who makes a recipe.
With the tab open, what arrives from the guild does not show up by itself: close and reopen the tab, or click a profession.