If a source evaluates or comments on the works of others it is considered a secondary or tertiary work. Read more about what constitutes a primary source, or an original work, so that you can tell identify one.
Websites are great resources but need to be carefully evaluated. Company websites, blogs by professionals, and gray literature are just some of the valuable resources you'll find on the web.
It's tough to find because it's not published and indexed in a traditional way, but this can be a gold mine! It includes things like technical reports, conference proceedings, committee reports, patents, etc.
Wentworth Institute of Technology