I haven't used Pinterest in years and may have accidentally clicked on a Pinterest result in Google search results and suddenly started getting all kinds of desktop popup notifications from them and don't know how or why.
They are (to me) one of the most user-hostile features chrome has added, because it's non-obvious what they are, and how to disable them. You can configure them somewhere in settings (I am on my phone right now).
chrome://settings/content/notifications