Itchy Anus is when there is an uncontrollable and unsatisfiable itchy feeling in the anus area. This could cause one to lose all focus on anything else going on because of its powerfull ability to annoy.
Jason: God Damn!! I am going completely mad! I have such bad itchy anus. I scratch and I scratch, but it doesnt seem to go away.
Pete:Well, be careful, don't scratch too hard or you might start bleeding.
Slimy Butt is when you can definately feel some moisture collecting in the butt crack, more specifically concentrated around the anus. Slimy Butt is most often caused by a poor job of wiping the butt after a poop. Slimy Butt often leads to Itchy Anus if not attended to.
Johnny-Boy: Aaahhh man, i had such a bad case of slimy butt i had to go wipe myself clean.
Todd: Good work Johnny-Boy, do you feel any better?
Johnny-Boy: You bet! I can finally walk around without an odd sensation in my crack.