What is the difference between optimizing and defragmenting my hard drive?

Optimizing a hard drive simply organizes the data so it can be accessed more quickly. Defragmenting a hard drive reorganizes the physical location of the data on the drive, so that files and programs open faster. Optimizing does not require moving pieces of data around, like defragmenting does. Fragmentation occurs when a file is too large to fit in one spot on the disk, though this is less common with newer drives.