What or Who can see me?

When you first login to a session, you will start fresh and clean, with no history for online sniffers to see. If you go to purchase online items, the moment you login into their site that site will know your profile that you created. Your location, history and data cookies will not available to them. Once you finish and start a new application, that history will disappear and the World Wide Web will be the less the wiser.

What or Who can see me?