Dude nothing is explained, during the entire move my wife and I are like are they good or bad aliens, throughout the entire thing they most of the times just not hurt people, for no apparent reason. In the middle of a fight and one stops and just scans looks and does absolutely nothing, and this is done over and over with absolutely no explanation.
Those ball thingys ran around and destroyed shit in the area, a freaking entire free way overpass making cars and people fall to their death but yet rolls up on a kid, stops and moves on. WTF.
And again there was no kind of attempt to communicate just lets just fuck them up from the get go. They (the aliens) did not even attack first, If I remember. I mean you meet an unknown ship that looks alien and fire a warning shot? ahahah.
ok ending rant