TO_CHAR() converts 12345.9067 to a string and specifies this number is to be converted using the format 99,999.99.
This results in the string returned by TO_CHAR() having a comma to delimit the thousands:
SQL> SELECT TO_CHAR(12345.67, '99,999.99') FROM dual;
TO_CHAR(12
----------
12,345.67
SQL>