Pilates strengthens the body but emphasises core strength (effectively your abdominal area and everything attached to it) to improve general fitness and wellbeing. Pilates exercises are done on a mat or using special equipment, such as the Reformer.
The reformer not only provides support for beginners and people with certain medical conditions such as scoliosis, spondylolisthesis and osteoporosis to limit the risk of injury, it can can also provide resistance for people looking to challenge their body more intensely.
Pilates has been used by dancers and particularly ballet dancers for years to improve strength with flexibility which complements their training by developing whole body strength and flexibility. In fact, many teachers are former professional dancers.