The provisional application was created to provide an inexpensive way to file an initial application for a utility patent. (Provisional applications for design inventions are not allowed.) To that end, it allows an applicant to file without providing all the information required for a standard patent application, such as patent claims, oath, declaration, information disclosure statement and all prior ideas that could be similar to yours.
So what do you get when you file a provisional application? For starters, you get to establish an early effective filing date on your invention, avoiding, at least for a while, the considerable time and expense of an official patent application. In effect, a provisional application holds your place in the patent application line.
This type of application also allows you to mark your product with the notice "Patent Pending" for one year, should you place your idea on the market. This notice serves as a warning to potential copiers that you are protecting your idea.
The provisional application for a utility patent also provides a quick and inexpensive way to test an idea's commercial potential before you make the expensive and time-consuming commitment involved in filing a formal patent. The fee for a standard utility patent is $380, while a provisional patent as an individual applicant costs only $75, and it gives you some security against having your idea stolen during its commercial promotion.
Unlike a patent, which is eventually disclosed, a provisional application is always kept confidential. Additionally, you could file many provisional applications for a patent on an idea and then consolidate them into one formal patent application within a year of filing the first provisional patent. This is of great benefit should you discover more patentable qualities after filing the initial provisional application: You won't lose the opportunity for inclusion as you would with a formal application, which can't be altered once it's filed.
A formal patent application requires all inventors of the idea to be included on the application. If you fail to include a name or wish to exclude a name, there's quite a bit of paperwork involved, which can prove to be expensive. With a provisional application, submission or omission of an inventor's name is simply achieved by the filing of a petition.
Should you decide, after one year, to turn your provisional application for a patent into a formal patent application, the result will be protection for 21 years from the provisional application filing date.