Also known as LEGO Draw.
LDraw is an open standard for LEGO CAD programs. It has become the de facto standard in the LEGO community, to the point where essentially all virtual models are rendered with programs that use the suite of tools the standard enables. It's only real competitor is LEGO's own LEGO Digital Designer. As such, it's one of the most important resources we index in our parts directory.
Swooshable use LDraw tools to create a lot of technique examples and render individual pieces. We also use some images to illustrate key LEGO concepts, for instance the illustration that describes the LDU unit on our introductory building article.