Finalized Submissions
API
When working with the API, there's one concept you should know about: finalization. With the simple POST form submissions, submissions are immediately visible in the Form Tools interface after the submissions is made. But with the API, it's a little more complicated. You would want, for instance, incomplete submissions to appear in the Form Tools interface before the user has completed all steps of the form. Similarly, what about people that started filling in a form but never completed it? In those cases, you wouldn't want to see.
To get around this problem, when using the API, you need to explicitly finalize the submissions. This is generally done on the final step of your form - or on the first, if you have a one page form. You'll read more about finalization in the ft_api_process_form() function and ft_api_delete_unfinalized_submissions() functions. For now, it's enough that you understand the idea!