Are you ready for some basic paragliding theory? Just like any other wing, a paraglider canopy moves through the air at a slight angle, called the angle of attack. Air flowing over the canopy is forced to move a little quicker than the air flowing under. This is because of the angle of attack, plus the top surface is more curved than the bottom surface. The air flowing over the top has a little further to go before it gets to the back edge, or trailing edge, compared to the air flowing under the wing.
OK, faster air on top, slower air underneath - this goes hand-in-hand with lower air pressure over the top and higher air pressure underneath.
Guess what? Yep, this results in an upward force on the wing called lift. Dragging anything through the air, even a wing, creates air resistance which tends to hold it back. This backwards force is called drag.
Now for some aerodynamic magic - lift divided by drag tells you exactly how well this wing will glide. It's called the lift-to-drag ratio, or LD. (Did you catch the inaccuracy in this bit of paragliding theory? Yep, the lines and risers, not to mention your own body, also contribute to drag!)
That brightly colored paraglider you saw over a sand dune last weekend might have an LD of 8 to 1, or 8:1. This means that if the wind suddenly stopped and the pilot flew it at its best flying speed, it would gently glide down, travelling 8 meters (or feet) across the ground for every 1 meter (or foot) of height it lost.
Currently, the very best competition paragliders can manage over 10:1. And in the world of open-class sailplanes, around 60:1 has been achieved! That is so flat, no wonder they can fly for 1700 kilometers (1000 miles) or more, on a great day, with a great pilot.
If you make a little paper plane and toss it carefully across your living room carpet, it might manage 3:1 or so. The best I ever managed as a teenager was a paper plane design that got just over 5:1.