This extension blocks trackers and cookies, which is pretty useful these days. It is not adblocker and does not have all the same features as uBlock. If someone would like all those features, they can use that instead.

The documentation is here:
https://support.startpage.com/hc/en-us/categories/5252303406100-Privacy-Protection-Extension

Lastly, yes System1 owns Startpage, but our commitment to privacy and more importantly our privacy policy have not changed.
https://www.startpage.com/en/privacy-policy