What is a PayPal Subscription, and does it cost to use PayPal with JotForm?

Please check this link for more details about what a subscription is: https://www.paypal.com/be/smarthelp/article/what-are-subscriptions-and-how-do-these-work-faq1916

Regarding the costs, JotForm does not charge fees for transactions, but the PayPal transactions may apply. JotForm will only limit the number of payments that can be received per month, you can find more details here: https://www.jotform.com/help/408-Understanding-Your-Account-Usage-and-Limits