Task based, or task oriented documentation is writing that takes you through a process/task step-by-step; it is succinct, lacks jargon, is easily understood, and structured entirely around performing specific tasks.

In order to get to Z, you need to:

  1. Step x
  2. Step y
  3. Step z

Keep in mind that people who need to know how to perform a task usually need answers quick!

Reference http://codex.wordpress.org/Glossary