A coupon is a code which needs to be applied at the checkout page to avail the discount whereas a deal is a discounted price on a product or a range of products.

To avail a deal or an offer customers need to simply click on the coupon and buy the product/service at the discounted price mentioned in the coupon.

To avail the discount via a coupon code customers need to click on the view code option and copy the coupon code. From there they will be redirected to the website. At the checkout page customers need to paste the coupon code click on apply to avail the discount.

Most brands allow only one coupon per order/transaction but this can vary from brand to brand.