Just as there are numerous types or workout available, there are also endless reasons why people train.
Just look around your local gym, or observe the runners or cyclists out in the street, and it will be obvious that there are a million answers to the question why people train. Many people exercise for a particular sport - to run the London Marathon, complete their first triathlon, improve their tennis game. Others simply want to get fit - lose a bit of weight, look better in a swim suit, or dazzle an ex-boyfriend at a big wedding.
But at other times, the answer to the question of why people train is more specific - for example, medical rehabilitation. Exercise is increasingly seen as a crucial part of preventing or recovering from illness, from heart disease to hypertension, asthma to diabetes. For many conditions, exercise can speed up recovery and reduce dependency on medication. Of course, some people have very specific goals when they work out. A great example is building muscle. Once just the provenance of gym rats and body-builders, building muscle is now seen as an important part of almost anyone's exercise programme - the exertion involved boosts the metabolic rate and is being increasingly recognised as an aid to weight management.
For most people, a judicious programme of weight training, combined with regular core training, will result in a stronger, healthier body, ready for whatever life throws at you, without a great increase in muscle mass. Many forms of exercise will provide this, with the added benefit of also improving flexibility - yoga and Pilates are two excellent examples of this. Pilates is also highly recommended for those who need postural correction. It's never too early to start - children need regular exercise, and with schools' schedules so restricted, it is incumbent on parents to provide both opportunities and a good example! So whatever your fitness needs, abandon the couch and start exercising - your body will love you for it!