Expiration dates are labels found on food and medicine that indicate the last date a product is guaranteed to be safe and effective. These dates help consumers know when to use or discard items to avoid potential health risks. For example, milk may have a "sell by" date, while medications often have a "use by" date, which is crucial for ensuring their effectiveness. It's important to note that expiration dates are not always definitive. Some products may still be safe to consume after the date has passed, but their quality might decline. Always check for signs of spoilage, such as changes in smell or appearance, before using items past their expiration dates.