Vacuum forming is a manufacturing process where a sheet of plastic is heated until pliable, then placed over a mold and vacuumed to create a desired shape. The vacuum removes the air between the heated plastic and the mold, causing the plastic to conform to the mold's shape. Once cooled, the formed plastic retains the shape of the mold and can be trimmed to produce the final product. This process is commonly used to create packaging, trays, and other plastic products with simple shapes.