Cauliflower is a member of the Brassica family along with kale, broccoli, romanesco and brussel sprouts.
Fun fact- cauliflower is actually the imature flower buds of the plant.

Steaming or stir frying the cauliflower preserves the most amount of nutrients. Roasting gives it that delicious nutty flavor.   The other parts of the cauliflower is also edible.  The stem (center) can be used in soups and roasted.  The leaves can be roasted like kale and used in soup and stir frys.

Cauliflower should be stored in a loosely sealed plastic bag with some paper towel to absorb an excess moisture.  Whole heads can be kept for 4 to 7 days.  Cut up florets should be used within 4 days.