It essentially means "all yours" or "completely yours". It's a way of expressing that something is fully at someone's disposal or that they have full control over it.
Here are some examples of how it might be used:
* "La maison est à vous entière." (The house is all yours.)
* "Le choix vous appartient à vous entière." (The choice is completely yours.)
* "La décision vous appartient à vous entière." (The decision is entirely yours.)
Note: You'll sometimes see it written as "à vous entière disposition," which means "at your complete disposal" or "completely at your service."