The term 'hatha yoga' covers all types of physical yoga. Placing an emphasis on postures with breathing and relaxation, it's suitable for all ages and levels of ability, making it ideal for beginners. Classes that are described as 'Hatha' tend to involve slow-paced stretching with some simple breathing exercises and meditation.
This type of hatha yoga is based on the guru/student model, in which an experienced teacher works with a student on an individual basis, making a personalised yoga programme based on their age, health, fitness and needs. While it still focuses on postures and breathing and concentration, it's ideally meant for those wanting an individual yoga programme for daily practice or a specific health concern.
This type of yoga puts an emphasis on postural alignment and poses or 'asanas' as a way of deepening relaxation. Physically demanding, it's most suitable for those with a reasonable level of fitness. Iyengar's method teaches a correct way to do each pose, sometimes through the use of props, such as blocks, straps, pillows and chairs. Once postures are done to perfection, the balance in the body is reflected in the mind.
Ashtanga uses a fast flowing, dynamic sequence of 75 poses (which take around an hour and a half to two hours to complete) with a focus on breathing. It's physically demanding, so is best for those who have a good level of fitness to begin with and enjoy a more athletic work out.