Online deals are much like the coupons you see in newspapers and magazines. The only difference is that you have the option to use it in online shops when checking out. Discount coupons have codes which you can enter in check-out counters, which will automatically take off prices on the items you're purchasing.
When you find a coupon, you can highlight and copy the code. Most codes, when clicked, will redirect you to the product for which the discount applies. Once you've clicked on the product, you can check out and paste the coupon code on the discount code box. The discounts that one can get from online coupons vary by product or store.