understanding partition tables

We are using db version 12.1.0.4

I am trying to understand the partition table concept. I want to do range partition for the tables to have the table partitioned by year. I can do the syntax for the existing data with the date. But, how can I make sure the future date entered will also be partition the same way? Or, do I always have to do this as part of maintenance every year to move the records around? Will there be a way this will be automatic partitioned for future data? Gurus, please advise. Thank you.

CREATE TABLE sales

  ( prod_id       NUMBER(6)