Processed food refers to any food that has undergone some form of processing such as freezing, canning, drying, or refining to improve its shelf-life, appearance, and taste. Other synonyms for processed food include convenience food, fast food, junk food, and packaged food. Convenience food usually refers to pre-packaged meals or snacks, fast food refers to quick and easy meals or snacks served in restaurants or drive-thru, junk food refers to high-calorie, low-nutrient foods with little or no nutritional value, and packaged food refers to food that has been pre-portioned, sealed, or labeled for ease of consumption. While processing can result in tastier and visually appealing food, it often strips the food of essential nutrients and introduces chemicals.