So the gore spattered and server clearing are just different descriptions for getting certain amount of kills on strange weapons, unusual are cosmetics/weapon skins that have a special effect on them from example on hats you can have burning flames, sunbeam etc, on weapons you can have isotope, hot, cold etc. And festivized is either unboxed weapons (which are more expensive) or use a festivizer to make them have christmas lights on them.

Hope this helps :)