What is a game time card?
Elder Scrolls Online is Subscription based MMO. That means you need to pay for the game time on monthly basis. If your subscription period comes to an end you can continue playing by purchasing extra months of game time. There are different ways to do it. You can pay directly from your credit card in your ESO account or you can buy a Time Card that gives you a definite period of free gameplay upon activation.
How the card works?
Time Card has a secret code that must be entered in a special field at your personal profile at the official website of the game. Once it is entered player receives extra game time.