As Windows starts it will read the configuration in the registry and know what drivers need to be loaded, what settings to be applied, and what resources need to be allocated in order for this equipment to work.
This allows Windows to retrieve that information at later dates such as when it is starting up. When a new piece of hardware or software is installed in Windows, it stores its configuration into the registry.
The registry is a key component of the Windows operating system, so much so that without it, Windows would not even run.
