multi page form, will it submit after each page?

I have a 3 page form and Will it submit after each page?

I'm afraid people will close the page before complete.

If the form has multiple pages, the form will not submit until the submit button is pressed at the end.  If you need to have each section submit on its own, separate the form into 3 different forms.  Then have each form lead to the next by changing the thank you page URL to the next form in your sequence:

http://www.jotform.com/help/211-Setting-Up-the-Thank-You-Page