The ad at the very top is Google AdSense. Right now, mine is showing an ad for woodworking tools, as I have been looking at them over the last few days. It isn't just your Google searches, any site that has Google Analytics reports to HQ who has been there. You might type in directly in the address bar "discountcameras.com", and you will start to see ads for camera gear, if that site had Google Analytics.
So that begs a question for the OP...