According to Joseph Wu, "Origami is a form of visual / sculptural representation that is defined primarily by the folding of the medium (usually paper)."
No one really knows when this art form was invented, only that it is an ancient art form that originated in Japan. In the late 1940s, New Yorker Lillian Oppenheimer saw an origami flapping bird at a family gathering and became enthralled by it. She began learning and teaching origami, and corresponding with paperfolders around the world. By 1980, her work, with the help of others, led to the founding of The Friends of The Origami Center of America, which in 1994 became OrigamiUSA.
The interest in origami today is widespread with many resources for enthusiasts. The first step in learning this art is to become familiar with the various folds. Next comes base figures, which are made from the folds. Base figures are the foundation for many structures. Once you can make base figures, you're ready for models!
If you're a beginner, try Paperfolding.com. Follow the instructions on the page and a pop-up window will open where you can click on Basic Folds. Here you'll find easy directions for fundamental folds, along with their names. Knowing folds by name will allow you to follow instructions for creating a sculpture.
Designating names to different folds is what makes learning and sharing origami easy. Without names, paperfolders would have to describe each fold in terms of corner, angle, direction, and so forth. It's much easier to simply say, "Make a petal fold," or "Follow that with a crimp fold."
After you've learned the folds, re-open the pop-up window and choose Base Figures. Base figures are noted as the starting point for many simple models. Each base figure is clickable and has folding instructions.
A great resource for practicing your paperfolding is Joseph Wu's site, where you'll find an entire page of origami sculptures from across the Web, most with simple folding instructions, just a click away.
Origami is an enduring art form — some say as old as the invention of paper itself in 150 A.D. Whatever its origins, it is certainly here to stay, and with a little practice you can join the millions of enthusiasts around the world celebrating the simple joy of paperfolding.