What does have your cake and eat it too mean?

You will not get what you want without giving something in return.

Meaning: To spend or used something up but still have it; to have two things when you must choose one.

Example: You can either go to a movie or get pizza, but you can't have your cake and eat it too.

Origin: This saying started sometime in the 1540's. Once you've eaten a piece of cake, you don't have it anymore. So you have to a make a decision to eat it or save it. In the same way, money that you've spent is money that you no longer have in your pocket. You have to choose what to do with what you have. The original version of this expression is"you can't eat your cake and have it too."