secure vs non-secure forms

So, what is the difference between the secure forms and non-secure forms?

For example, if a user fills out my form with his personal info (address, phone, etc.) will it be safe for him to do so via a non-secure form?  In other words, will his info be transmitted safely to me?

Hello ssmediator,

Please be noted that if you use SSL, the submission data is encrypted while it is being transmitted from your form to our server. 

The submission data will definitely sent to you safely but if your form contains sensitive information, you should always use SSL version of your form. The following guide should help you on how to receive SSL submissions:  http://www.jotform.com/help/63-How-can-I-receive-SSL-Submissions

Hope this answers your query.

Do get back to us if you have any questions.

Thank you!