Components are React components used for composing the UI of Calypso.
They come with their own styles defined according to our guidelines, and manually loaded from the styles assets folder. Structuring the user interface with these building blocks has several benefits — like allowing to quickly construct a view that is visually consistent with the rest of Calypso, and easier to iterate on.
Many of these components can be seen in action in our DevDocs: UI Components section.
Read documentation on components for more in-depth information.