The secret is that there isn’t one thing called documentation, there are four:
Tutorial
- is learning-oriented
- allows newcomer to get started
- is a lesson
Analogy: teaching a small child how to cook
How-to guide
- is goal-oriented
- shows how to solve a specific problem
- is a series of steps
Analogy: a recipe in a cookery book
Explanation
- is understanding-oriented
- explains
- provides background and context
Analogy: an article on culinary social history
Reference
- is information-oriented
- describes the machinery
- is accurate and complete
Analogy: a reference encyclopaedia article