Compositing node

Support Basics & Interface
1

I was looking some artworks, and there is some discussion about compositing node. What is that and what is it used for?

2

An explanation is probably useless without pictures anyway, so here’s the ‘official’ description from when it was introduced with 2.42:

http://www.blender.org/development/release-logs/blender-242/blender-composite-nodes/

3

a very good link, thanks