Basically, it's things that you as a user won't "click on". You want to have a computer that supports it, because more and more apps in the future will make use of these APIs. Without support for them, you either won't be able to use those applications at all (if they're actually _about_ those filters and effects) or you simply will get a version that blinks and glitters less.
Currently, the Dashboard has a Core Image effect when adding a widget. It ripples the screen. If your computer does Core Image, that is.
In my understanding, it is the modernisation of rendering effects on screen. powerful new technologies that make it far more efficient and faster to manipulate images, video and audio on a completly hardware level.
it's the underlying technology between the hardware and the screen. it's what the computer is doing. like replacing old joists with shiny, stronger new girders.
Core Video is basically Core Image...for video. Yeah. I think they use all the same effects. They're both easy ways for programmers to manipulate images using highly optimized routines that take full advantage of your system's graphics card. The result is pro-quality effects that are craaaazy-fast, that any developer can use with very little effort. We haven't seen a whole lot of programs that use them yet, but the number is bound to grow.
Like I said, Core Image is optimized for graphics cards. Only newer graphics cards are supported, however. It WILL all work on ANY system, mind you, but without a newer graphics card it just won't be so fast. So real-time effects like Dashboard's ripple will only really work on systems with newer graphics cards. Aside from speed, though, the results should be identical on all systems.
All the Core technologies have flexible plugin architectures, so third-party developers can create their own routines that, when installed, will become available to all other Core Audio/Image/Video-aware programs.