A "join" is a term commonly used in databases to combine data from two or more tables based on a related column. This allows users to retrieve meaningful information that spans multiple datasets, making it easier to analyze and understand relationships within the data. In programming, particularly in languages like SQL, a join can be categorized into different types, such as INNER JOIN, LEFT JOIN, and RIGHT JOIN. Each type specifies how to handle records that do not have matching values in the joined tables, thus providing flexibility in data retrieval.