Refactoring improves the structure of code without changing the functionality of the application.
@tunixman: So is refactoring really refactoring if there are no UnitTests?
@bigballofmud BrianFoote: Technically yes, but so is blindfolded brain surgery.
You unit test guys crack me up. You're like heroin junkies, but funnier.
See WhatIsRefactoring for a more complete description and explanation.