Rendering also applies to 2D graphics and compositing artists. Essentially, if you have to create anything visual within the computer, you have to render it. Whatever you create within the program of your choice (from Lightwave to After Effects), if you want to turn it from a set of computer parameters to an actual image or series of images, you must render it.
With modern computers, you do not have to stop everything to render a shot or image. I am well known among my friends for posting to E2, posting to my blog, writing, Photoshopping, and many other things while rendering relatively complex effects shots in Adobe After Effects, Discreet Combustion, as well as other motion graphics applications. Your computer may slow down, as mine does, but such multitasking is possible and, in my view, totally encouraged.
I would have encouraged nEoN nOoDlE to update his or her own WU on this subject, in lieu of my contribution, but it appears that he or she has not been on E2 for quite some time. I'm working on a revision of this WU that will cover the information from his/her WU.