Compound components share implicit state while giving consumers flexibility.
Example: Accordion
<Accordion>
<Accordion.Item>
<Accordion.Header>Section 1</Accordion.Header>
<Accordion.Panel>Content 1</Accordion.Panel>
</Accordion.Item>
</Accordion>
How it works: The parent Accordion manages which item is open. Children access this state via context. Consumers control structure; the compound manages behavior.
When to use: Components that are meaningless alone but powerful together. Tabs, accordions, menus, select dropdowns.