how are they launched?
Different methods, namely aerotowing, winch launching, bungee launch etc.
Gliding
In an aerotow a powered aircraft is attached to a glider with a tow rope. Single-engined light aircraft or motor gliders are commonly used.
how long do gliders stay in the air They can stay airborne for several hours. what is gliding? It is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. who created the first glider? The Germans when? In  the 1920s and 1930s how do they fly? Through air that is ascending as fast or faster than the glider itself is descending, thus gaining potential energy. what's the fastest they can go? UNANSWERABLE so you mean they use lift to fly? Yes, ridge lift, wave lift etc.
wiki:14186541
Gliding [SEP] Aerotowing
In an aerotow a powered aircraft is attached to a glider with a tow rope. Single-engined light aircraft or motor gliders are commonly used. The tow-plane takes the glider to the height and location requested by the pilot where the glider pilot releases the tow-rope. A weak link is often fitted to the rope to ensure that any sudden loads do not damage the airframe of the tow-plane or the glider. Under extreme loads the weak link will fail before any part of the glider or plane fails. There is a remote chance that the weak link might break at low altitude, and so pilots plan for this eventuality before launching.