These models fly freely without any means of control. The skill lies in trimming the model on the ground to fly in a controlled manner once airborne.
Models range from simple chuck gliders, through tow-line and bungee launched gliders, rubber, C02, electric and diesel/glow I/C powered propellor driven aircraft, as well as Jetex and Rapier (a form of jet propulsion). There are categories for indoor and outdoor flight, as well as sport, duration and scale type models.
For the beginner free flight offers perhaps the most economic introduction to aeromodelling - for less than the cost of a 'Big Mac' at MacDonald's you can construct a simple model with the potential to fly out of sight and be lost forever!!