Ever wondered how IKEA comes up with those awesome room ideas you see in their catalogue and on their site? Well a lot of those room ideas are completely made up and are instead 3D renders, not photos.
IKEA didn't want to photograph every piece of furniture and build entire rooms which take a lot of time and aren't very environmentally friendly. Instead they came up with the genius idea of using computers and very talented artists to render a lot of what you see in their catalogues and on their site. This process makes it much easier and faster to change any elements they don't like and make everything look perfect.
The renders are so incredibly detailed that you can even see the grains in wood and the thread in a pillow. They wanted to make everything as realistic as possible. Now 75% of the products you see in the catalogue are completely rendered and they are constantly trying to up that number.
CGSociety published a much more detailed look into how it's all done, you can read it on their website.