Said as an expression to signify when there is indeed a difference between two things or situations, but that difference is unimportant or negligible. Often used when someone is making a big deal out of an insignificant difference. Can also be used to indicate indifference between two choices.
Origin of the phrase: Generally, if someone wants a cheeseburger, and they're served a hamburger, they won't fuss or complain. Sure, there's a difference, but who cares? It's a slice of cheese. Your life's not going to end because you didn't get cheese. Get over it.
Panama City or Myrtle Beach? Hamburger cheeseburger. (Beaches, who cares?)
or
$300, $299? Hamburger cheeseburger. (It's a dollar.)
or
Burned to death, smoke inhalation, hamburger cheeseburger. (He's still dead).
While Johnny Welfare plays acid rock on a stolen guitar, his old lady has a better idea...
That's right, she's got the munchies for a CaliforniaCheeseburger.