Canning jars are glass containers designed for preserving food through a process called canning. They come in various sizes and shapes, typically featuring a wide mouth for easy filling and cleaning. The jars are sealed with a metal lid and a rubber gasket, creating an airtight environment that helps prevent spoilage. These jars are commonly used for storing fruits, vegetables, jams, and sauces. The canning process involves heating the jars to kill bacteria and enzymes, ensuring the food remains safe to eat for an extended period. Popular brands of canning jars include Ball and Mason.