Any public disclosure of your product (which could be as simple as a demo to potential investors not under NDA or a YouTube video), "publications" including web pages, and "offers to sell" which may include advertising. Announcing the name of your product probably is not a problem, but a splash page that describes how it works or on boarding users could make your idea public. The details can get tricky.

If you think you might want a patent, don't hesitate to talk to a patent lawyer to make sure you are not waiving your rights, otherwise you'll regret it. You can always choose not to spend money on the patent application but make that decision after you know what you are doing.