All you need to know is that you should choose the option "without OIDS". If you wish to understand why, continue reading. OIDS are used by PostgreSQL's system tables. They refer to tables, types of data, etc. OIDS were created for system tables only, and should not be used for user tables. Unfortunately, some coders started using OIDs as default primary keys. If PostgreSQL removes OIDs, the applications coded by these guys would crash. So for the sake of backward compatibility, there is now an option "without OID".