Yoga means “Union” in Sanskrit - Union of Body, mind and Soul.
Its also called "flow", one of the most popular contemporary styles of yoga focusing on smooth flow of poses.
It is focused on awakening of the 7 Chakras, hence more spiritual than physical.
Bikram Yoga is a system of hot yoga to extract the sweat benefits and more flexible body due to heat, it was devised by Bikram Choudhury
This is more for fitness enthusiasts and excellent for fitness. It started as Ashtanga but changed for western students.