CCleaner is a software tool designed to optimize and clean up computer systems. It removes unnecessary files, temporary data, and browser history, helping to free up disk space and improve system performance. The program is available for both Windows and Mac operating systems. In addition to cleaning, CCleaner offers features like a registry cleaner, which helps fix issues in the system registry, and a startup manager that allows users to control which programs run at startup. Overall, it aims to enhance the efficiency and speed of computers by maintaining their health.