Many large corporations have both Corporate Development departments and Venture Capital arms in order to handle opportunities to work with and/or acquire small companies. I'm not sure specifically how Amazon does this, and there is really no "standard" approach. Many companies have different venture groups under them with obscure names meant to sort of hide them from view. Otherwise many people would reach out directly and they would be swamped with deal flow that was not highly qualified.

Have you actually built anything or is it an idea only? I would say it's unlikely to attract their attention unless you have significant traction and you can clearly demonstrate how it fills a hole in their offerings or their portfolio, or that you are important to acquire so that a competitor does not acquire you first.

Most of the answer will depend on the details, I'm afraid.