A release candidate is more finished than a beta. While a beta is still a work in progress, a release candidate is "this is what we are going to release unless you can find some bugs before the release date". Of course, it is impossible to state which will be the last release candidate, because that would mean you knew which bugs existed and how easily you could fix them, in which case there'd be no need for a RC.
Gold refers to the release version.
"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)