There are several reasons why you may want to file a provisional patent application before filing a full non-provisional patent application.
Whereas a full patent application (non-provisional) takes a professional several weeks to properly draft, a provisional patent application can often be filed within 1 day. A quick filing allows you to obtain an early filing date for your invention. Filing dates are often used to establish who was first to invent something.
Compared to a quality non-provisional patent application which can cost thousands of dollars, a provisional patent application is considerably less expensive. If money to submit a full patent application is an issue, the provisional application still allows you to secure a filing date for your invention as you gather the capital necessary for a quality full patent application.
If you are not yet certain you wish to protect your invention, a provisional patent can first lock in your filing date for 12 months, should you decide to use that date later on for a full patent application. Within these 12 months, you can market your idea to companies, manufacturers, establish your business plan, or simply gain insight from friends and family. Should you conclude that your invention is worth protecting, you can then submit a full patent application which can claim the filing date of your provisional patent application. See an example of this in the article Patent Filing Dates.
Having the legal term “Patent Pending” on your invention can be extremely valuable for two reasons. First, it serves as deterrence to people who may want to mimic your invention. Placing the term “Patent Pending” on your invention communicates to others that an official claim has already been placed on the invention and could lead to eventual protection by patent rights. Second, it serves as a marketing term to show customers that your invention is unique and steps have been taken to protect that uniqueness.
For a more detailed understanding, see Understanding Provisional Patent Applications