Partitioned tables are not processed by autovacuum.

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/15/runtime-config-autovacuum.html
Description:

There is a statement in the Postgres Docs: "Partitioned tables are not
processed by autovacuum."
https://www.postgresql.org/docs/15/routine-vacuuming.html

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?

I found the above statement unclear.