Over time your hard disk drive can get fragmented. You’ll begin to notice that opening applications and saving files take a little longer than they did before. Disk defragmentation only applies to hard drives with mechanical spinning disks (HDD).
If you have a solid state drive or SSD, then you don’t need to worry about defragmentation. Defragging has no effect on performance with a SSD. Windows 10 will usually detect a SSD and optimise the drive using the TRIM command rather than defrag.
Select the drive you want to optimise/defragment. Click the ‘optimize’ button.
This will start de-fragmenting your disk. This process can take a while.