What is a Google Engaged View?

Question

I just became aware of this https://support.google.com/google-ads/answer/9149284?hl=en 

Google is passing back to MMP a click for a 10 second video view. Is this something new? Or has it existed for long time?

• Our system will now count an ‘Engagement’ whenever a user clicks or watches 10 seconds or more of your TrueView for action ad using maximize conversions or target CPA bidding. 
• By default,  a ‘Conversion’ will be counted when a user takes action on your ad within 3 days of an ‘Engagement.’ You can ask your Google team to customize this time frame if you prefer an alternative.  

And how do we check how many engaged views we have per campaign?

Answer 1

Engaged View means that the viewer watched the ad until the very end. Google also has some metrics for measuring views to other waypoints in an ad:

From this page.