In traditional origami, Valley Folds and Mountain Folds have been included.
Valley fold - Folding is done following the dash line " - - - - ", and folding downward (as if into a valley). You may either fold left to right or vice-versa.
Mountain fold - Folding is done following the dash-dot line " - . - . - ", and folding upward (as if creating a mountain). The crease will be on the top and the paper is folded behind. The letter “M” above the “dash-dot” is for improved visualization.