The custom email links generated by Marketing Cloud Account Engagement are tracked for link clicks, page visits and email opens. Link clicks are recorded when a prospect clicks on a link in an email. Page visits are recorded when a prospect visits a page on your website that has the Marketing Cloud Account Engagement tracking code. Email opens are recorded when a prospect opens an email and downloads the invisible image that Marketing Cloud Account Engagement inserts in the email. Form completions and unsubscribes are not tracked by the custom email links, but by other methods.