Section of Backstage where Frontend Managers edit global Pages.
In the Master App you can create Layout templates (Blueprints), Kits that can be reused across your Pages and Master Pages that are used across your site, e.g. Search, Checkout, My Account, Error Pages, Category Pages, Product Details Pages etc.
Below is an example of what you will see when you first open the Master App:
"In the Master App, I've added a new Blueprint Layout for our Pages as well as creating a Kit for the Header. I've also created a new Checkout!"
For more info, see the Using the Master App article.