Surprisingly, there are some users who still, in the year 2016, don’t understand what disc defragmentation is, or even how they should go about doing it. That’s fine; this post isn’t here to judge, but to educate.
Basically, overtime your computer starts racking up a bunch of files or bits of files (fragments) that clutter the background of your computer’s storage. This can chew through your finite amount of storage, as well as absolutely kill your computer’s performance. These fragments appear from everyday use: updating programs, installing new programs, moving/deleting/creating files, and more. What happens is residual files and pieces of files start to collect, much like a trash can in real life; although you empty your can, you’ll almost always find some piece of trash sticking to the bottom.