How is the meningococcal vaccine different from the meningococcal meningitis vaccine?

It isnt: They are the same. They mean the same vaccine. There are two brands however, Menactra and menveo, but they are essentially approved for the same purpose with slight differences only.

The same: A vaccine is a set of proteins that trigger your body to produce antibodies against a certain agent. In this case it is the agent that causes Meningococcal infections. The most serious Meningococcal infection is the one that involves the meninges of the brain. This becomes Meningococcal meningitis. Good antibodies that build up from the vaccine can protect against the meningitis.