"Supplementary material" refers to additional information or resources that support or enhance the main content. It provides extra details, examples, or explanations to give a more comprehensive understanding of a topic. Full definition
Provide these types of clients with plenty of supplementary materials outlining the details of the properties you are introducing to them. (baylor.edu)
See supplementary material for more detailed age, gender and breed information (Table S1). (link.springer.com)
However, an online driving course can benefit a new driver with supplementary material to prepare for the written exam for a license. (dmv.com)