Thermals are rising columns of air created by convection heating. Birds have been using this source of lift to gain altitude for a long time and now the r/c glider flyer can have access to this free source of energy. R/C models can be launched in to the air by the aid of high start, winch and aero-tow and then released to search for thermals.
RES stands for Rudder-Elevator-Spoiler -- the simplest form of RC glider control. The RES class is for those who enjoy flying polyhedral type airplanes with a minimum of controls. A computer radio is NOT needed; in fact a 2-4 channel radio and a well designed plane are all that is required to be competitive.