Cache-Control is an HTTP header used to specify how web browsers and servers should handle caching of resources. It helps control the storage of web content, allowing developers to define how long a resource can be stored and when it should be revalidated. This ensures that users receive the most up-to-date content while optimizing loading times. By using different directives within Cache-Control, such as "no-cache," "no-store," or "max-age," developers can fine-tune the caching behavior. This is crucial for improving website performance and managing bandwidth, as it reduces unnecessary requests to the server for unchanged resources.