A product network is a network of retail items. Network nodes in a product network represent items purchased by individuals and co-occurring in their shopping baskets or carts. You can connect two product nodes if customers often or always buy the respective products together. We call such products complements. Left and right shoes (if sold separately), nuts and bolts, nails and hammers, and one-way airline tickets from Boston to Seattle and from Seattle to Boston are good examples of complements: when you buy one, you almost always buy the other as well.
Product networks can (but do not have to) be weighted: you can define the weight of the edge as the frequency of co-purchasing. You can slice (Slice Weighted Networks