Via Ars Technica:
If you haven't been following this, [Topics] will track the web pages you visit and generate a list of advertising topics that it will share with web pages whenever they ask, and it's built directly into the Chrome browser.
To turn it off, go to
Chrome Settings > Privacy and Security > Ads Privacy and Disable Ad Topics, Site Suggested Ads and Ad Measurement.
But if you can, switch to Firefox - it's not perfect, but it's gotten much better since Chrome's launch and it won't mess with adblockers!