The first is the idea of having optional content. In previous versions of adobe captivate you could simply select one of your smaller breakpoints and place optional content off the stage and into the scrap area. When these projects were displayed on smaller devices the optional content would not be visible, yet that content remained for larger displays.
The second idea relates to grouping a series of objects together for alignment purposes. Sometimes you might have several items that need to stay aligned regardless of screen size. In the past grouping these objects together made keeping all the items aligned. Of course in Captivate 2017 grouped objects are not compatible with fluid boxes, so how can we do something similar.