As far as I understand, this is about declarative partioning. So you don't have to implement all the details yourself anymore, you just declare how a table should be partioned instead of defining tables, triggers, ...
Note that there is no shorthand syntax (yet), where you define a partitioned schema in just one line of DDL.
As of now, you still need to create the root partitioned table as one command specifying the partitioning method (list or range), partitioning columns (aka PARTITION BY LIST | RANGE (<columns>)) and then a command for every partition specifying the partition bounds. No triggers or CHECK constraints anymore though. Why that way? Because we then don't have to assume any particular use case, for which to provide a shorthand syntax -- like fixed width/interval range partitions, etc.
That said, having the syntax described at the beginning of the last paragraph in the initial version does not preclude offering a shorthand syntax in later releases, as, and if we figure out that offering some such syntax for more common use cases is useful after all.
