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 seal, creating an airtight environment that helps prevent spoilage. These jars are commonly used for storing fruits, vegetables, jams, and sauces. They are often part of home canning kits, which include tools like canning lids, canning rings, and pressure cookers. Properly sealed canning jars can last for years, making them a popular choice for food preservation.