These are both field values listed in your viewing reports:
Embed Tracking indicates where the activity originated for a user, i.e. if they registered/viewed on the BrightTALK website or another website. This can be used if you would like to know which websites are hosting your content.
The below articles explains how to embed on your channel:
Embedded URL allows you to track the usage of any customised URLs your audience has clicked on to reach the webinar. This can be particularly useful for gauging the success of individual email marketing campaigns based on co-marketing arrangements. Embed Tracking can be implemented by modifying the standard audience viewing URL. For information on how to do this, please see the below article: