The Registry is a hierarchical database that stores configuration settings and options on Microsoft Windows operating systems. It contains settings for low-level operating system components and for applications running on the platform that have opted to use the Registry. The kernel, device drivers, services, SAM, user interface and third-party applications can all make use of the Registry. The Registry also provides a means to access counters for profiling system performance.
When using adding and removing programs items in the regestry are created moved and sometiems left behind. Cleaning a registry is one way to help improve computer performance and even combat some software related issues and errors.