Our data source is Wikidata, a structured data project similar to the encyclopedia project Wikipedia. Each item is identified by a Q number, and information can be added directly to an item's page (in this case, https://www.wikidata.org/entity/Q127745). Some information however, like an author's papers, are stored on the item for the paper itself. The "What links here" link in the sidebar of an item can show these items.
There are also various tools available which can make editing Wikidata quicker and more rigorous.
Most important for Scholia is the Author Disambiguator, which can be used to quickly create new dedicated items for authors and find existing papers which do not link to the author.