Fitness vs Health

Fitness and health are different things.

Fitness is more specific, and describes how good you are at an activity.

The better your cardiorespiratory fitness, the better your heart and lungs can cope with maintaining endurance activities like distance running, or, in a different capacity, the quicker you can recover from short, intense bursts of activity like sprints.
Your ability to deadlift a heavy barbell is a different kind of fitness.
Your ability to hold a yoga pose is yet another kind of fitness.
Your ability to balance on one leg is arguably another kind of fitness.

Fitness in a given area is improved by training specifically for that kind of fitness.
A sprinter, a distance runner, a strongman, and a yogi all have different physiques and different skillsets because they train for different kinds of fitness. Training for any given one of these skillsets can be to the detriment of the others.

For example, a sprinter is ideally muscular to produce power, in contrast to a distance runner who ideally weighs less for efficiency at running long distances.
Both sprinter and distance runner will take advantage of tight muscles and connective tissues in the legs and calves, which provide mechanical efficiency by acting like springs during movement; in contrast, a yogi would be hindered by such tight tissues.
A yogi would ideally be flexible throughout the hips and shoulders, allowing them to get into advanced yoga positions; however, for a strongman excess flexibility would be at the expense of joint stability, meaning his risk for injury would be higher when lifting something heavy and awkward, especially whilst already tired.

Health is a measure of how free from and resistant to disease and injury you are. It also suggests how long you might live.

A healthy diet and sleeping pattern protect you from diseases of malnourishment and chronic stress.
Healthy bones, muscles and joints are less prone to disease and sudden injury.
Posture and movement patterns can be considered healthy or unhealthy. Slouching on a sofa or swivel chair for multiple hours at a time is an unhealthy practice that can lead to chronic or acute low back pain through adaptive muscular imbalances.

There is much overlap, but pursuing fitness to an extreme typically compromises health – being the best at a given physical activity will come at a cost to the athlete’s health.
For most people improving their own health is a more fitting goal than setting a record, and this is achieved with a healthy balance of exercise, diet and lifestyle choices.

Knowing what your goals are is an essential first step in improving your health and/or fitness.