Body Mass is a measure of an individual's weight relative to their height, and it takes into account factors such as muscle mass, bone density, water content, and fat. It can be used to determine body composition, which in turn can help individuals understand how much they weigh compared to others with similar characteristics (such as age or sex). Body Mass Index (BMI) is a commonly used measure of body mass that takes into account weight and height to give an indication of whether someone has a healthy weight for their height.