Splash screen is a funny name for the little graphic that shows the progress of the KDE Desktop as it loads after you have logged in. Each of the icons is animated or flashes in its turn as KDE progresses in loading. There is also a text and bar type progress indicator at the bottom of the Splash Screen.
The Splash Screen page gives you a few choices for your splash screen. This feature is nice to have and changing it might make the wait for KDE to load and initialize a little more pleasant for you, but it is a trivial thing. Play with the options on the Splash Screen page if you wish, but I generally leave it alone.
The Splash Screen usually changes from one release of Fedora Core to the next, as it is part of the visual signature of each. It still performs the same function in each release.