A Disk Defragmenter is a utility tool used in computer systems to reorganize fragmented data on a hard drive. When files are saved, deleted, or modified, they can become scattered across the disk, leading to slower performance. The defragmenter consolidates these fragmented files, making them easier for the system to access, which can improve overall speed and efficiency. Running a Disk Defragmenter is particularly beneficial for traditional hard disk drives (HDDs), as they rely on physical movement to read data. However, it is generally not necessary for solid-state drives (SSDs), which use a different technology that does not require defragmentation. Regular use of a defragmenter can help maintain optimal system performance.