CLASSES.zip is a release file of the Minecraft mod Wandercraft, made for Minecraft 1.0.0. It was published on September 17, 2012 and is 1.3 MB in size. For the full description, screenshots and every other version, visit the Wandercraft mod page.
How to install: Put the .jar into the mods folder (.minecraft/mods) and start Minecraft with the matching mod loader profile.