What is an opportunity cost?

An opportunity cost is the cost you pay when you give up something to get something else.

An example of this, is when you want to buy a new video game, but you also want to buy a new music CD, you will have to give up one thing for the other in some cases.

I have done a lot of this in my life, since I'm poor, I don't have enough money to buy two things at once, I have to sacrifice one thing for the other, and someday, I can buy the item I gave up.