When you open up the Info Panel, you'll see the engagement data breakdown. The most important split here is always Web Shares vs On-Post Engagement (Posts). 

Web Shares refer to the number of times a particular article/URL has been shared on Facebook. The vast majority of these will originate from people using the Facebook share button directly on the publisher's website.

On-Post Engagement refers to the likes, comments, reactions and shares generated directly on social media posts on social platforms.
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For example, on Facebook posts we include these engagement metrics:

If you would like any further clarification on these or any other terms, please be in contact!