A greenhouse is a structure designed to create a controlled environment for growing plants. It is typically made of transparent materials like glass or plastic, allowing sunlight to enter while trapping heat inside. This helps maintain a warm temperature and protects plants from harsh weather conditions, pests, and diseases. Greenhouses can vary in size, from small backyard setups to large commercial facilities. They are often used to grow a variety of plants, including vegetables, flowers, and herbs. By providing optimal conditions, greenhouses can extend the growing season and improve crop yields, making them valuable in agriculture and gardening.