A co-citation is one of the citation metrics defined as the frequency with which two documents are cited together by other documents. More co-citations imply a stronger subject similarity between these two documents.
Many SEOs believe that co-citation is of the many factors that influence how Google understands web pages, the relations between them, and their relevancy.
Starter
See what people search and spy on competitors.
Webmaster Tools
Get Ahrefs data on your site and fix what matters.