Can a person start a form, stop and go back and finish?

There are actually a couple different ways of allowing users to save and continue forms.  The first involves allowing the user to submit a partially completed form and sending them a link in an email to allow for them to return to their specific submission to update it:

https://www.jotform.com/help/40-How-to-Let-Users-Update-Their-Form-Submissions-at-a-Later-Date

The second method is a bit more complex.  It requires using two forms, one to send an email with a session URL and a second form that needs to be multiple pages:

https://www.jotform.com/help/97-How-to-Save-Forms-and-Continue-Later

I usually recommend the first as it is quite easy to set up and and the edit link does not expire.