On what services do I have to pay for?

As far as I am concerned, making a Jot account doesn't bill me right? What can I do with a free account and how is it different from a paid one?

To create an account you don't have to pay. We have different plans depending on your needs. You can read more about the plans in this link

The main difference it's on the number of submission, storage etc.

Let us know if you have any other question.