From BlenderWiki

Reference

This is the type of doc useful to learn:

• very GENERIC and LIMITED things,
• small actions not related each others (no workflow)

Examples

• how does UI Blender work?
• what's a context in blender? what is an obdata?
• what is this button for?
• which button does action X?
• which is the shortcut for action X?
• where is the button in the UI?
• in which context I can use it
• how many states has this toggle? which are default/max/min values?

Car metaphor

• how to turn your car's wheels,
• how to put in first gear,
• how to change a wheel,
• how to change the fuses of the car
• ...with plenty of time

Manual

This is the place where we look into the documentation about

• GENERIC, SEMI-COMPLEX actions
• involving a LIMITED WORKFLOW (you probably stay in 1 or two editors in Blender)

Examples

• How do I do box modeling vs polygon modeling in Blender?
• How do I setup a domain for fluids?
• How do I edit strips in the sequencer?

Car metaphor

• how to start uphill,
• how to drive in a desert city (no cars/people in the streets, easy!)
• how to drive on the snow, or by night, or in a highway,
• ...with plenty of time

Which means that to do the task you have to :

• understand how Blender works in general and its basic concepts
• know where to find things
• do many small actions in different areas and editors

that means also that you have read a REFERENCE or, just in case, it's have available to refresh ideas when needed.

Tutorial

This is where people asks about:

• SPECIFIC and COMPLEX tasks
• involving a COMPLETE WORKFLOW (you use a lot of editors and features in Blender)

Examples

• How do I model/texture a tree of the type X?
• How do I model, texture, light and render an eye?
• How do I model and rig a cat and then animate it to do a walk cycle?
• How do I setup my pipeline in a animation or video editing job?

Car metaphor

• TASK: you have to take your girlfriend at the restaurant for your anniversary, ok you know how to drive your car but....
• ...it's a cloudy night, and she lives in a big and crowdy city,
• ...it starts snowing right while driving on the last hill before the restaurant!
• ...and now you have a punctured wheel!
• (for the sake of argument, you might still have plenty of time ahead and she still smiles at you adorably :)

To accomplish this task you have learnt a lot of things before (in the walk cycle example, maybe the tutorial isn't about modeling but you still have to model the cat).

Tech/Theory part

This is the part where you already are in control of Blender, but in order to choose the tool you need to know what happens in the code.

Examples

• you have a very bad greenscreen and none seems to work, so you need a combination of Difference and Chroma nodes, and you would really like the formulas behind them.
• you wanna know more about how to use premul and key alpha in a particular situation, say texturing
• you wanna know the algorithm behind some physic simulation
• you wanna know more about how Blender saves PNG, because the UI doesn't show the level of compression for example.

Car metaphor

• how does my engine work?
• which kind of snow tires is better?
• I wanna use GPL fuel in my car, how?

Current wiki implementation

I've setup a theory section in wiki, crosslnked from the Manual, but it has been a failure by now.. See http://wiki.blender.org/index.php/Doc:Theory --> 3 pages as today...