The landing page can be enabled or disabled in your project dashboard. When you go to the Landing Page tab you can customize things such as the header and body content.
This will be the title text that goes into header.
This will be the text that goes underneath the promo title, but it will still display in the header.
Underneath the promo title and text, you will have the option of having Nothing, Buttons, Search Bar, or Custom HTML. Custom HTML will override your promo title/text as well, so keep that in mind when editing.
You have many templates for your body content and you can add more than one if you want to display multiple templates on your landing page.
This will be the default if you do not select any of the options. It will display documentation, announcements, and the forums.
If you have any of these three features disabled, you should not use this as it will link your users to a 404 page.
This simply lists all your categories with quick links to doc pages. You can also choose to display the reference section as well.
Three columns of text, text, text + media
These let you add the text yourself that you want displayed as well as uploading an image to display.
If none of these suit your needs, you can always add custom HTML to get it exactly how you want it.