Explanation:

If you want to test new marketing content based on web conversions, such as orders placed on your website, you should configure Web Conversion as the engagement metric in Path Optimizer. This allows you to track how many subscribers completed a web action after receiving an email from each path. Email Engagement is used to measure opens and clicks on your emails. Manual Engagement is used to manually select the best path based on your own criteria. You can learn more about this in the [Path Optimizer] module on Trailhead.