Autovacuum on Partitioned Tables

There is a statement in the Postgres Docs: "Partitioned tables are not processed by autovacuum."

What does the above statement mean?

Does autovacuum not process both the parent and the child tables in a partition relationship? 

What is the definition of a partitioned table?

I have a table with 50+ million rows that gets data added to/wiped from it every 90 days. We are planning to break this table into a few thousand partitions. More partitions will likely be added in the future, but we don't have plans to delete any of the partitions. Will we need to manually track the statistics of these partitions and manually vacuum the tables or will autovacuum help to manage them?

Best,
Ryan