Whats the difference between render layers and render passes ?

Support Compositing and Post Processing
1

I mean i know i can put one object in layer1 and another in layer2 and add diffeent postprocessing fx .

But what are render passes ? and render i’ds ?

is there a video tutorial on that ?

thanx

2

With render layers
http://wiki.blender.org/index.php/Manual/Render_Layers
you can control what is being rendered, i.e. turn some objects in you scene on or off in a single render.

Render passes
http://wiki.blender.org/index.php/Manual/Render_Passes
are how many times the colour of a single pixel is calculated.

In the render layer panel you can turn various render passes on and off to speed up a render.

There is a good introduction to all this at
http://blenderunderground.com/2008/03/31/introduction-to-composite-nodes-part-1/

Hope it helped
/ Mats