Soaring is flight powered by the air that the airplane travels through. Rising currents of air, whether caused by wind deflected by a cliff or mountain, or whether bubbling up from warm ground, can lift an airplane to great heights, and keep it aloft for hours at a time.
Birds use this source of energy; the circling hawk rises in thermals over the deserts; the seagull glides along cliffs and in front of ships; the wandering albatross can surf the air pushed along by waves at sea.
R/C Soaring uses small (and not so small) aircraft, controlled by radio signals, to exploit the same energy for fun and for competition. R/C Soaring pilots compete to stay aloft the longest, or for precise periods of time; they seek speed both against the clock and against each other; they fly aerobatics; and they fly just for the sheer fun of watching a plane dance among the clouds.
Soaring has the unique property that each flight is an individual challenge in and of itself. You must find lift every time, or you will come down.
At first it seems impossible that a plane can be supported in invisible air and then you find that first thermal, or toss a plane off a cliff and then, like magic, it rises.