Das ist ein...
Bottleslingguy!
It is a way to take advantage of the 12-month U.S. grace period, which allows an inventor to publicize, advertise, use or sell his/her invention before filing for a U.S. patent on it. In a way, it's like a provisional filing in that it gives you a "trial' period to explore your options before incurring the cost of a regular patent application.
The 12-month period is fully independent of the 12-month period given with a provisional filing. Technically, an inventor can enjoy almost 24 months of priority, before filing a regular application.
A pro-active publication can be made in print, on television, on the internet, and so on. It must disclose enough detail about an invention that someone else can appreciate the inventive step (in layterms).
It doesn't provide patent pending status on its own. But, it can be used to establish priority without question. Large companies sometimes prefer this method over filing patents for incremental improvements to their own product or service lines. And, since it costs little or nothing, it can be a powerful tool for the independent inventor.