Different ways of having video content at your fingertips without having to deal with physical media. You can do this in a lot of different ways, with servers and distribution, large DVD changers with libraries controlled externally, etc.
I use a fairly simple DIY method sort of like the kaleidescope system. I rip all my DVDs onto server storage, and have a front end that lets my go through the library of movie cover art/descriptions on my main HTPC, and then click and watch it in my theater. Right now I'm actually only using the main PC, but a big server with a TB or more is in progress soon, to stream all the stuff over a simple LAN. DVDs are sooo passe....
