A Provisional Patent Application (PPA) is a document filed at the patent office that describes your invention, but it may or may not contain claims and is a less formal document than a patent application.
A provisional patent application gives the applicant the benefit of a priority date and 12 months to apply for a regular patent application. You must file the regular patent application within 12 months, otherwise benefits of priority date will have to be forgone.
The requirements for a provisional application are lower than that of a regular patent application. The PPA should include a complete description of your invention. It should explain in detail the working of the invention and how to make the invention. The description should be supported by drawings wherever required.
PPA gives you benefit of a priority date when applying for a patent, but it need not eat into the 20 year term of your patent. Taking priority from a PPA can still give your patent a 20 year term from the date of filing.
Thought the PPA does not give you any rights as a patent does, still you are allowed to use “Patent Pending” notice as soon as you file a PPA.