What is a "partitioned view"?
Partitioned views are a (very) old technique for partitioning data that are very rarely used today.  Oracle added the ability to partition tables back in Oracle 8, which provides much more functionality than partitioned views, at which point partitioned views became obsolete.  The only reason to consider using partitioned views would be if you can't afford a license for the partitioning option and you're willing to accept the reduced functionality and extra maintenance required to use partitioned views.  The documentation on partitioned views will pretty much all date back to the Oracle 7 days.

In order to use partitioned views, you would define individual tables for each logical partition, create a CHECK constraint on whatever column you want to partition on so that the optimizer knows which table a particular row must be in, and then create a view that does a UNION ALL on each table to create the partitioned view.  Queries against the partitioned view using the partition key can then be resolved by the optimizer to access only one of the physical tables comprising a particular logical partition.

Of course, if you use this technique, you have to create a new physical table and rebuild the partitioned view every time you add a new partition which is quite a bit of maintenance.  Getting the partitioned view to work correctly and making sure that partition pruning is happening correctly is much, much more challenging than when you're using a partitioned table.  Plus you end up with a ton of separate tables with very similar names polluting your namespace.