Understanding what it means to be "bound"

I found this great post that shows, in simple language, how computer work is “bound:”

“Most of our daily tasks are IO-bound, including anti-virus, backup, database, and file copying.

Microsoft Office is human-bound. A faster computer won’t help you to type faster.

Photo, video, and audio related tasks (such as format conversions) are CPU-bound, as well as gaming and any kind of 3D work.

In summary, your tasks can be IO-bound, human-bound or CPU-bound.”