This is the opening to Gears of War 3, which very briefly retells the events of the first two titles while setting up this latest installment. Suppose I was bound to stop watching that .GIF of Cliff Bleszinski getting celebratory Gears-themed cake on his nose eventually.
If for some reason you're on a media blackout (Do people actually do that for this series?), I wouldn't worry too much here -- it's basic information on what went down between the previous game and now. Spoiler warning: they give away the origin story for the Lancer with spray paint on it.
Doesn't do much for me personally, but I am really looking forward to the single-player portion of Gears 3.