This is the software publisher’s description.

Hard disks are by far the slowest component in your computer, particularly if you’re a laptop user with a 2.5” drive. CPU and memory work much faster than hard disks because they do not have moving parts. Therefore fragmented disks often become a bottleneck of the system performance.

Besides causing slowdowns, fragmentation makes the hard drive disk heads move frequently when reading files which leads to freeze-ups and system crashes. It is important to keep your disks defragmented and optimised as much as possible.
Disk fragmentation leads to system slowdowns, PC crashes, slow startup and shutdown and sometimes to system failures.

Auslogics Disk Defrag is designed for fast optimisation of today's modern hard disks. Get the maximum performance out of your expensive hardware investment.

The latest version includes support for defragmenting removable drives, such as a USB stick and other devices. Other improvements for Vista and general program stability.