What is Disk Defragmenter?

Disk Defragmenter analyzes local volumes and consolidates fragmented files and folders so that each occupies a single, contiguous space on the volume. As a result, your system can access files and folders and save new ones more efficiently. By consolidating your files and folders, Disk Defragmenter also consolidates a volume's free space, making it less likely that new files will be fragmented. The process of consolidating fragmented files and folders is called defragmentation. The amount of time that defragmentation takes depends on several factors, including the size of the volume, the number and size of files on the volume, the amount of fragmentation, and the available local system resources. You can find all of the fragmented files and folders before defragmenting them by analyzing the volume first. You can then see how fragmented the volume is and decide whether you would benefit from defragmenting the volume. Disk Defragmenter can defragment volumes that are formatted with the file allocation table (FAT) file system, the FAT32 file system, and the NTFS file system. As a result, your system can gain access to your files and folders and save new ones more efficiently. By consolidating your files and folders, Disk Defragmenter also consolidates the volume's free space, making it less likely that new files will be fragmented. Using Disk Defragmenter will help speed your computer. (How to Speed Up your Computer and How to Use Disk Defragmenter)

Definition of Terms:
Fragmented – The scattering of parts of the same disk file over the different areas of the disk. Fragmentation occurs as files on disk are deleted and new files are added. It slows disk and degrades the overall performance of disk operations.
Volume – An area of storage on a hard disk. A volume is formatted by using a file system, such as FAT or NTFS, and has a drive letter assigned on it.