Your hip is the area of your body at the top and side of your thigh, beside your pelvis. You might have a habit of closing the refrigerator door by bumping it with your hip.
Your hips are the flesh between your waist and upper leg, and they're also the bones that make up the complex joints there — the ones that make it possible for your legs to move so you can walk. When a person is described as hip, it means they're trendy or cool, up on the latest thing. These two meanings are unrelated, with the "cool" meaning coming from the slang hep, popular with jazz musicians around 1915.