A gift card is unlike a gift voucher, which can be purchase and send to the person whom the customer wants to send the gift. The gift voucher recipient can purchase the products from your store using that gift card.
When the customers want to purchase some gift for someone special, but they don't know what will be the recipient choice. So they can buy a gift card with particular amount which gives full freedom to the recipient to purchase the product using that gift card.
The customers can gift the gift card to his loved one, and they can reedem it whenever they want. There is no expiry date for the gift card.