The `UPDATE ... FROM` clause is a powerful SQL feature that allows you to update rows in one table based on data from another table. Instead of manually specifying each row to update, you can use a `SELECT` statement to identify the rows that need modification. This is particularly useful when you need to synchronize data between tables or perform bulk updates based on criteria from another table. It's important to understand that the `FROM` clause in this context refers to the table whose data you're using to update the target table, not a join operation. The `WHERE` clause is still crucial to specify the exact rows to update. This method is more efficient than using multiple `UPDATE` statements or a loop in your application, as it's handled entirely within the database engine.