To put it another way, the SQL standard doesn't guarantee any particular ordering. This does not mean that table storage must be unordered: it means that a database can store them in any order it wants, which might not be any order at all, or it might have some particular kind of order which the DB depends on to do its work.

But as a database user, you cannot count on that order matching what you, personally, would have implemented if you'd had a chance. ORDER BY clauses allow you to tell the database to sort the results of a query according to something appropriate for your particular needs, but this has no effect on how they are stored.