What does “Auto-renew” mean?

Auto-renewal means that when the current subscription expires, the next subscription will be automatically selected from the available subscriptions. The next subscription must be identical to the current subscription.

If an identical subscription is not found, auto-renewal will not take place and your backups may fail. No subscriptions will be bought automatically. Only those subscriptions available at the time of auto-renewal can be used. You can select auto-renewal for each individual subscription or set up bulk auto-renewal of all of the activated subscriptions you have.

What does "Auto-renew" mean?