Functional training is an over time proven method in training or rehabilitation of athletes, astronauts or special forces, which according to the requirements of their industry had to develop specific skills and qualities.
Functional training trains complete body movements, as opposed to isolating one muscle at the time, like bodybuilding routine. This provides you better muscular balance and joint stability, while decreasing the chance of injury. Lean and defined muscle tone is achieved throughout functional training, because of the multitude of directions and multitude of muscles and stabilizers utilized during each exercise.
Let's not neglect the "fun" factor, regarding the complexity and diversity and the multi-plane movements used during the exercises, which integrates also the brain in training by utilizing a large variety of functional instruments: medicine balls, suspensions, (TRX, gymnastics rings), VIPR, Bulgarian bags, ropes, climbing wall, dumbbelles, Olympic bars, barbells, Bosu, obstacles, plyometric boxes, Kettlebells, etc.
Functional training is a thing for everybody, from the beginners to professional athletes, young or senior, being adaptable for everybody's target or aim.