It's the feminine singular form of the French word "carte," which can refer to various things like:
* A playing card: "J'ai une carte d'as." (I have an ace card.)
* A map: "J'ai besoin d'une carte pour aller à la gare." (I need a map to go to the train station.)
* A credit card: "J'ai payé avec une carte de crédit." (I paid with a credit card.)
* A business card: "Donnez-moi votre carte." (Give me your business card.)
So, the exact meaning of "une carte" depends on the context of the sentence.