Just with John's patenting frenzy alone you've learned about divisionals, C-I-P's and reissues. You also learned a little about provisional and nonprovisional applications. But, there is more. Continuing applications are another application type that can be used.

Essentially, they are a second application for the same invention claimed in a prior nonprovisional application.

A continuing application must be filed while the parent application is pending. In addition, it must claim the benefit of the parent under a domestic priority claim.

Continuing applications must disclose the same subject matter as the original. You can have as many continuing applications as you need; a second, third, even fourth application by the same applicant for the same invention is possible. However, continuing applications must disclose the same subject matter as the original and must be filed by the same applicant.

So why use a continuation application? Perhaps the prosecution isn't going well and the original application needs to be scratched and re-written. In instances like these, a continuing application can serve to be highly useful. 

One important note to make is that parent applications are never abandoned when a continuing application is filed since the continuing application will claim the filing date of the original.