Manufacturer Coupons can be found in national coupon inserts in newspapers, direct mail, magazines, package inserts, internet printables, through surveys, mail-in forms, and often accompany samples that you receive in the mail. Usually the manufacturer will pay the face value of the coupon directly to the store.

Retailer/In-Store Coupons are coupons offered directly from the retailers and can be found in sales ads, direct mail and internet printables.
Electronic Coupons are coupons that are available from retailers and manufacturers that can be loaded onto a loyalty or shopper card such as a Kroger Shopping card.

Peelies are coupons attached to the product, generally wanting you to use it during that purchase. Etiquette says to only take those that are afixed to the products you're purchasing.
Internet Printable Coupons can be printed off the internet. They will have a unique serial number for each print if they are a legit coupon. For a list of Coupon Sites click HERE
Electronic Coupons are coupons that aren't physically in your hand but rather loaded on a loyalty card or prompted with your phone number.