A provisional patent application is a 12-month place-holder for a utility patent. The USPTO allows you to label your invention as Patent-Pending during this 12 month period. If a utility patent is not filed within the 12-month period, your spot in line is lost! Once the utility patent is filed, your utility patent filing claims the patent priority date as the provisional filing date. The patent priority date is the date from which you have a legal claim as the first inventor to have invented the subject matter of your patent application. As such, the patent priority date is an important factor for the examination process through which the utility patent undergoes.
The provisional patent application never gets examined for patentability, it only serves as a place holder for examination – however, the patent examiner will carefully scrutinize the content of the provisional patent application during the non-provisional patent application process. So it’s important to have your provisional patent application compliant with all applicable laws in order for it to preserve the patent-priority claim – otherwise, the Examiner can withdraw the patent priority claim and inventors are put in a bad spot, thinking they were patent-pending during the provisional patent process when in fact their patent pending status gets withdrawn upon the examination of the non-provisional utility patent application!
So, a provisional saves your spot in line for a utility patent. It is especially important in our first-to-file patent system. It is especially important as you market and as you share your invention/idea with engineers, developers, or those with deeper pockets than you! It always preserves your claim to the invention as those engineers/developers further improve on the invention.
If you are interested in more detail related to your situation it is best to speak with an attorney.