I found this interesting article in Science Daily that notes confusion over date labeling leads to billions of pounds of food waste every year. Below is a brief explanation of each. I was throwing away food that was most likely perfectly fine to consume because of the date noted on the packaging.
Use-By: This label is aimed at consumers as a directive of the date by which the product should be eaten; mostly because of quality, not because the item will necessarily make you sick if eaten after the use-by date. However after the use-by date, product quality is likely to go down much faster and safety could be lessened.
Sell-By: This label is aimed retailers, and it informs them of the date by which the product should be sold or removed from shelf life. This does not mean that the product is unsafe to consume after the date. Typically one-third of a product's shelf-life remains after the sell-by date for the consumer to use at home.
Best-By: This is a suggestion to the consumer on which date the product should be consumed to assure for ideal quality.