Many databases "tag" or add terms to the articles -- similar to tagging pictures in Facebook.
The agreed-upon, standard terms used in library catalogs and databases are called subject headings or descriptors.
The subject headings in a catalog or database record will often help you locate more books/articles that are similar. It works much as "find more like this" or "find similar" links do elsewhere.
Searching in full text databases often retrieves many things that seem unrelated. The search engine is finding the words, but they are far apart in the document. Proximity operators help solve this problem! These tell the search engine to return results when two words are within x number of words of each other. So Wilmington n5 riot, retrieves newspaper articles with these words within 5 words of each other: race riot in Wilmington, Wilmington North Carolina rocked by riot, etc.
The abbreviation used as a proximity operator varies from one database to another. When you are in the database, look for the "help" button to find specific search tips.
If you are searching within the full text of older materials, remember that terms used and their spelling may have changed:
In the online versions of some older texts, the scanning technology cannot accurately reproduce damaged text, so the search function may not be optimal.