The purchase of one copy of a program entitles the purchaser to install the software on one computer. The software must be uninstalled from a computer before installing it onto another.
The purchase of a classroom license entitles the purchaser to install the software on an unlimited number of computers as long as they are all in the same physical room. If you purchase a classroom license for a program bundle, you can break up the bundle to different rooms as long as one specific program is installed in only one classroom at a time. It pays to purchase a classroom license if your room has 3 or more computers that would would want to install a program on.