I use DuckDuckGo search and when I went to whatismyipaddress.com using Tor browser, some ads by Google popped up:
Is my anonymity being compromised?
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This site and many others show advertisement. The task of Tor Browser is to make sure that those sites can't access your information. So they can't access cookies which come from other tabs or sessions. So using Tor Browser strengthens your anonymity.
When you close the browser and re-enter the website, it looks a new visitor went to the site. This is because the site has no information about former sessions and cookies.