The most basic of all filters in many graphics editing software, it blurs adjacent pixels to a varying degree to create a very smooth image. Compared to real camera out of focus blur it looks very artificial. Some teenage girls use Gaussian Blur on their Myspace angled portrait photos to hide their ugly pores and pimples ending up looking silly, comparable to a man with a plastic mask and a vendetta.
You gotta be kiddin' me! Nobody is going to believe that the Gaussian Blur you just applied is real! You should have used the Lens Blur instead for more realistic look.
The out of focus blurry areas in a photo, usually referred to as bokeh. Depending on the camera and lens, the blurriness may either be a visually pleasing eyegasm or just a gruesome and brutal rape of your eyes.
Sweet, the bokeh on this photo is so creamy! I wish the lens blur on my camera was this awesome, but the aperture on this cheapo lens only goes up to f4.5 :(