The various folds are the building blocks of origami, they are what turns a flat sheet of paper into a intricate work of art.
There are many different used folds in origami, this site currently only covers four of them. Some are probably used in almost any project, such as the mountain and valley folds, while others are reserved for more complex models.
The two most commonly used folds are the valley and mountain folds.
The Valley fold gets it’s name from the fact that when unfolded, it’s fold line sinks into the paper. It is created by folding one edge of a piece of paper over the other.
The mountain fold is the inverse of the valley fold, in deed, if you turn the paper over, any mountains will look like valleys and any valleys will look like mountains. When unfolded, the mountain appears to rise off the paper. To create this fold, you have to fold one of the edges under another edge, or, if you find this to difficult, you can just make a valley fold on the other side of the paper, since the two are inverses.
The diagonal fold is a commonly used and simple fold. To create it, fold the paper such that one corner meats the corner on the opposite corner, for example, the top left corner meats the bottom right. (when the paper is folded along the crease, the paper will be shaped like a right triangle, and when it is unfolded, there should be a fold line running diagonally through the center of the paper.
The squash fold is a pacific type of fold used on two layered triangular flaps, like the ones fond on the preliminary and water bomb bases. It involves lifting the flap in question, separating it’s two layers with your fingers, and then pushing down the top crease of the flap so that the flap is squashed into a flat triangle, with two new flaps on each side. (Click on the squash fold link to find a example of the squash fold in a model)