Google quietly announced on Google+ the addition of three new columns to the AdWords reporting dashboard for AdWords Display reporting for those who use Lightbox ads.

The new columns are Engagements, Engagement Rate & Average CPE. In short, they just renamed other metrics to these new names:

Expansions will be moved from “Clicks” to the Engagements column.
Expansion rate will be moved from “CTR” to the Engagement rate column.
Average cost of expansions will be moved from “Avg. CPC” to the Avg. CPE column.

In addition, the Click metrics columns (“Clicks,” “CTR,” and “Avg. CPC”) will now refer to clicks from the Lightbox ad in its expanded state to a landing page.

Forum discussion at Google+.