database_properties are the permanent properties, ie, those used when the database was created.

v$parameter represents those in use in the current instance (or current session), eg

SQL> select value from v$parameter where name = 'nls_date_format';

VALUE
--------------------------------------------------------------------------------
DD-MON-RR

SQL> alter session set nls_date_format = 'yyyy-mm-dd';

Session altered.

SQL> select value from v$parameter where name = 'nls_date_format';

VALUE
--------------------------------------------------------------------------------
yyyy-mm-dd

1 row selected.