How can I get clarification about the JotForm plans?

Also, what does available space mean? Is this space on your server for our forms? Also, what happens when the monthly views or the available space are exceeded?

Please clarify these terms. Thanks.

The available space is the one that you use when you get file uploads through your forms, you could get free space by deleting those submissions where you received file uploads. 

We have also some options to download your files so you do not lose the information, please check these guides that will help you with that: 

https://www.jotform.com/help/356-How-to-Download-the-Submission-Files 

https://www.jotform.com/help/374-How-to-export-all-of-your-data-at-once 

When you reach the available upload space you will notified through the "My Forms" page, you could also delete the files, as explained above, in order to keep receiving more uploads. 

Regarding the submissions limit, when you reach it, your forms are disabled and you will need to either wait until the limit resets on the first day of the next month or upgrade your account to the next plan. 

You could also complete the tasks under the Get More section of your account so get more submissions for free. 

https://www.jotform.com/myaccount/getMore 

I hope this helps.