This does one, simple thing but it does it well. It simply places one sequence after another. Of course it would be possible to do this by laying them both over each other using a Merge node and then TimeOffset one input. However, that is two nodes, not one.
The Cross Dissolve parameter will do exactly as it says. This will, in effect, shift the second sequence backwards in time so that it overlaps the first.
The Fade In and Fade Out parameters will fade in the first sequence and fade out the second. Not wildly useful.
There is an example of this node in action in the assets of Lesson 5.