In Australia, the main source of lift, as glider pilots call it, is from thermals, which are created as hotter air rises away from the ground. Another less common form of lift is wave lift, where a strong wind blowing against a mountain range rises over the mountains and form waves of rising air behind the mountains. In wave lift, gliders can climb to very high altitudes. Another form of this lift is called ridge lift, where wind blows along the face of a ridge, allowing gliders to fly along the ridge and climb. Frontal lift, where two air masses of different temperatures and densities meet, can also sometimes be found, but is not a reliable source of lift.
Gliders do the same when in lift.
If the feather falls out of the rising air that you created, it starts falling down again. Now consider a room full of people blowing - a glider flies around the sky looking for these areas of lift, and then tries to stay in these areas. When a glider finds an area of rising air, the pilot will try and spend as long as possible in that air. If the lift found is from a thermal, the pilot will circle in the rising air. This act is called thermalling.