When drafting a symmetric pattern, patternmakers only make half the garment. Some pieces get cut as a left and right side (like a sleeve) while others get cut mirrored (like a center front). This ensures that both sides of the garment will be identical when they are supposed to be.
When sewing for yourself or making one sample, many people will cut “on the fold” so that they can cut both sides simultaneously.
When it comes to production, though, factories don’t cut on the fold. They lay out the whole width of the fabric in many layers and use the whole pattern piece. When cutting many garments, you can nest the patterns more closely along the full width and still get your cutting efficiency by cutting multiple layers at once.
CAD pattern softwares will let you mirror the half piece that was drafted to create a whole. This mirrored whole piece is what is used in a production marker for the cut layout.