A "JOIN" is a fundamental operation in databases that combines rows from two or more tables based on a related column. This allows users to retrieve data that is spread across multiple tables, making it easier to analyze and understand relationships within the data. Common types of joins include INNER JOIN, LEFT JOIN, and RIGHT JOIN, each serving different purposes in how data is combined. In a typical scenario, a JOIN might be used to link a table of Customers with a table of Orders. By doing this, one can see which customers made specific orders, providing valuable insights into purchasing behavior and customer preferences.