A "filly" is a young female horse, typically under the age of four. This term is commonly used in the equestrian world to distinguish young females from colts, which are young males. Fillies are known for their playful and energetic behavior as they grow and develop. In horse breeding and racing, fillies can be trained for various disciplines, including dressage, show jumping, and racing. As they mature, fillies may be bred to produce offspring, contributing to the equine population. Proper care and training are essential for their growth and development into healthy adult horses.