A gym – physical exercises and activities performed inside, often using the equipment and following a strict plan of training and eating.
A gym is a gymnasium, also known as a health club and fitness centre. Gymnasiums have moved away just being a location for gymnastics. Where they had gymnastics apparatus such as barbells, parallel bars, jumping boards and running path etc.
If you are looking to join a gymnastics club, please see gymnastics.
A health club, a fitness centre is now commonly referred to as a gym.