The `IDENTITY_INSERT` command in SQL Server is a DDL command that temporarily disables the automatic generation of identity values for a specified table. This allows you to explicitly set the values for the identity column during an INSERT statement. This is often used when importing data from external sources or when you need to control the sequence of identity values. It's important to note that `IDENTITY_INSERT` is a table-level operation, meaning it affects all rows inserted into the table until you turn it off. This is different from setting the `IDENTITY_SEED` or `IDENTITY_INCREMENT` which are specific to the table and column. Using `IDENTITY_INSERT` is a powerful tool, but it's crucial to understand its temporary nature and the potential for data integrity issues if not used carefully.