A skit is like a mini scene acted out. And Interlude can be anything...a skit, a short song, a speech. Those Keith B-Real Interludes could be considered skits. Same with the interlude after "Potnas," that could be a skit also.
While we are on this topic. U can tell when an artist simply can't put a quality album when their are just as many interludes on the album as their are songs. However, i really like the way Heavy D's "Blue Funk" and how Rakim's "The 18th Letter" have interviews laced thru' out the album. It just makes it so much more personal.