Are you flexible? Can you touch your toes? Do a back bend? Make yourself into a pretzel? If you can, then your muscles are flexible.
Being flexible is important because your muscles are less prone to injury. Bending and stretching your muscles keeps them strong and pliable.
Some exercises increase your muscles flexibility like yoga, ballet, and gymnastic. The more often you stretch and bend the more flexible you will become. This flexibility can also help you do well in other sports and activities.