All coupons fall into one of two categories; manufacturer or store coupon.
Manufacturer Coupons: Produced by the product manufacturer and can be used anywhere the product is sold. Can be found in the newspaper, online and on/in the product itself.
Store Coupons: Produced and distributed by a certain store (ie: Publix, Target, CVS) and can only be redeemed at that specific store. Can be found in store circulars, store fliers and store websites.
Best part of this: Most stores will let you "stack" a manufacturer coupon with a store coupon. If you can pair that with a good sale, you can usually get that product for a really great price.