A FULL OUTER JOIN is a type of database operation that combines records from two tables, returning all rows from both. If there is a match between the tables based on a specified condition, the corresponding data is merged. If there is no match, the result will still include the row, but with NULL values for the missing data from the other table. This join is useful when you want to see all information from both tables, such as when comparing two datasets like customers and orders. It helps identify records that exist in one table but not the other, providing a comprehensive view of the data.