The following is a quick summary of the three kinds of packaging that, when combined, make up the entire packaging line. Primary packaging : This is the primary layer, which contains the final product, such as a plastic bag containing whole-grain cereal or a shoebox containing a shoe. Secondary packaging: Outside principal packaging, this form of packaging is used to group a specific number of items into a stock-keeping unit. Tertiary packaging: This form of packaging is used to convey greater amounts of transit packaging from a manufacturing site to a retail location.