You lose weight when the number of calories you burn working out is more than the number of calories you intake. You burn fat by exhausting yourself and letting your body consume the stored fat. Typically in a gym, the cardiovascular exercises can be very monotonous and boring that's why many people look for fitness workouts outside of the gym. Aerobics and Zumba are right up there when it comes to people's choice for weight loss.
A 1 hour Zumba session involves continuously moving your body in Latin American dance movements (specially selected strenuous ones) that make you sweat, exhaust you and help you burn fat. What's most amazing is that you enjoy it because you're dancing throughout.