Many people have heard a snap or a pop come from their hips from time to time. This can happen when they're doing something that puts a lot of stress on the hips or if they've been injured. While snapping hips can be harmless, they can be caused by injury as well.
Snapping can occur when your hip bends and the band of tissue that runs along your hip to your shin passes over your thigh bone. That band might catch, causing the snapping sound. If this happens often enough, there can be swelling and this can cause pain. You could also get the snapping from a tear in the tissue in your hip, or by the tension of a tendon as it's stretched across the thigh bone.
Many people will hear the snap and think it odd, but won't go to a doctor because they aren't feeling any pain or discomfort. If your hip is bothering you, it's best you see your doctor so you can be checked to be sure it's not something serious.