Run the statements in the right panel.
The accounts table contains an account number that is generated by default, rather than generated always. This means that a user could supply an account number if they wanted to as part of the insert statement.
The 'default' keyword tells DB2 to insert the default value into the database, rather than one that is supplied. This keyword is required since a NULL value is different from a default value.
Select from the account table to see what the results are. In this example, two values should have been generated by DB2, while the rest are set by the value in the insert statement.