Literally it means 'blank/white card' in French; it is used in several languages (not only English) to describe giving unconditional authority to someone; 'to give a carte blanche' means to give someone full liberty in choosing ways of achieving a goal.

Hi dear :), we use to say that in Italian too... when we tell someone 'I give you charte blanche on this', we mean 'you are free to do what you want with this' Just think, if you think about what a 'charte blanche' materially is you can realize that it's a simple white paper sheet. No instructions on it, you are free to do or write what you want :). So,with a charte blanche, as we say 'dare carta bianca', you give full liberty to someone about something. I hope you can understand:)

Carte Blanche is possibility of free action, free hand, unlimited power of attorney received from someone