A half-fold is created by folding a page in half, creating 4 panels.
A tri-fold (or “letter-fold”) is a popular type of folding pattern for letters and brochures. The printed material is frequently divided into 3 sections of approximately the same dimensions and then folded along these lines into thirds, creating a 6-panel finished piece. Z-fold (or “accordion-fold”) is an open variation of a tri-fold.
A double-parallel fold is often used for legal (14") paper. The 14" length is folded in half to 7" and then in half again in the same, parallel direction. The final folded size is 3.5" x 8.5". When used for brochures, this fold pattern lends itself to 4 sections per side, or an 8-panel finished piece.
Creasing (or scoring) is often required before folding color print jobs to avoid paper “cracking.” Creasing is almost always needed when folding heavy cover stocks.