Carte blanche is complete freedom. If a dozen seven-year-olds were given carte blanche to spend the day doing whatever they wanted, things might get a little crazy.
When you have carte blanche, pronounced "cart blahnch," you're free to do whatever you want. It was originally adopted by English speakers to mean "blank paper," and grew to have its current meaning in the late 1700s. One of those blank papers might be a check that can be made payable to any amount. So if your wealthy aunt offers to take you on a carte blanche shopping spree, it means she'll buy you whatever you like.