Before anything else, origami is made of two folds. The mountain fold and the valley fold are the alphabet of the craft - every crease you will ever make, from a simple square base to an intricate bird, is one of these two directions or a combination of both.

This quick overview shows them side by side in two photos. A mountain fold bends the paper down so the crease rises like a peak; a valley fold bends it up so the crease dips like a valley. Once you can tell them apart, every diagram you follow will suddenly start to make sense.

These are the two basic folds in origami. Pretty much every fold is either a mountain fold, a valley fold, or a combination of the two.

With a Mountain Fold, the crease bends the paper down and the crease resembles a mountain.

With a Valley Fold, the crease bends the paper up and the crease resembles a valley.