The automatic renewal means you will be billed for your access to the software on a monthly / annual basis, or every 3 years, i.e. your credit card will be charged every month / every year, or every 3 years automatically.
After the expiration date of your subscription, the system will automatically renew it for another billing period (month / year / 3 years).
The pros here are that it saves you time and effort by not having to make а new purchase every month/year/3 years and also ensures your work is uninterrupted.
You can turn off the automatic renewal until 30 days prior to your renewal date for yearly subscriptions (and 14 days for monthly subscriptions) by logging into my.chaos.com
You can enable the auto-renewal again until the renewal date is reached. Please note that it is not possible to reactivate your license once the end date has passed.