Cauliflower is one of the several cultivars of the species Brassica oleracea, Brassicaceae family. Similarly to broccoli, it is composed by a large flowering head. White is the most common color, but there are also orange, green, and purple cauliflower varieties.
Cauliflower is sometimes used as a lighter substitute for potatoes or rice: it is low in carbohydrates but high in dietary fiber, and can produce a similar mouth feel. Cauliflower also is low in fat, and rich in folate and vitamin C.
In cooking, Cauliflower is usually steamed or boiled, and then seasoned in a pan with other ingredients. It is considered a great side dish, but you can also make a soup, or a pasta dish.
Fun fact: during cooking, Cauliflower emanates a strong smell, due to the high sulphur content. To obviate this, just put in cooking water some bread soaked in vinegar.