A rewards card is a card that is swiped along with a credit card during a purchase to earn you extra points or money. Many department stores offer rewards cards that accumulate points if used with your purchase at their store. These points from your rewards card can then be exchanged for products or discounts on other products from the store.
Rewards cards are also often offered by credit card companies to entice customers. A prime example of this use of rewards cards is flight rewards miles. Credit card companies may also team up with another company to offer a credit card that has an affiliation with the third party company. An example of this would be a credit card company offering an electronics company credit card, with the rewards card providing "dollars" spendable on any product from the electronics company.
While rewards cards may seem like a bit of a hassle, the benefits make them more than worthwhile.