Registry cleaning is the process of scanning and removing unnecessary or outdated entries from the Windows Registry, a database that stores settings and options for the operating system and installed applications. Over time, the registry can accumulate errors, such as broken links or invalid entries, which may slow down system performance or cause software issues. Using a registry cleaner tool can help automate this process, identifying and fixing these problems to improve system efficiency. However, it's important to use reputable software, as improper changes to the registry can lead to system instability or crashes. Regular maintenance can help keep your computer running smoothly.