"Priority date" is a very important concept to learn if you are interested in patents. The priority date proves
when you came up with your invention. It is like a place holder for your idea. It is important because if another inventor comes up with the same idea, the priority date will decide who had the idea first.
That's why we think filing a provisional patent application with the U.S. Patent and Trademark Office is the way to go. It sets your priority date - it sets your official date of invention. If you publicly disclose your invention, that becomes your priority date.