docs: add descriptions for each main heading in o2 storybook composition

apps/o2-storybook-composition/stories/home.stories.mdx

@@ -9,3 +9,21 @@ Storybook for Origami 2 components from all brands. Browse all components using
 Storybook is still work in progress project and not all components have demos. If you don't find the component in storybook, for the moment you will need to reference the [Origami Registry](https://registry.origami.ft.com/components) instead.
 
 For support, please contact us in the #origami-support Slack channel.
+
+## Categories
+
+### Brandless
+
+Any components which have no brand styling. Typically, libraries and any components that do not use any of the following brands.
+
+### Core
+
+FT.com's main branding. This includes sub brands such as professional.
+
+### Internal
+
+The main brand used on internal applications.
+
+### Whitelabel
+
+Components with lightweight, minimal styling.