Disk cleanup is a process used to free up space on a computer's hard drive by removing unnecessary files. Over time, computers accumulate temporary files, system files, and other data that are no longer needed. This can slow down the system and take up valuable storage space. By performing a disk cleanup, users can delete these files, helping to improve the overall performance of their computer. Most operating systems, like Windows and macOS, offer built-in tools for disk cleanup. These tools scan the hard drive for files that can be safely removed, such as temporary internet files, recycle bin contents, and system error memory dump files. Regularly using disk cleanup can help maintain a computer's efficiency and prolong its lifespan.