It's the final game in the trilogy revolving around the endeavours of Commander Shepard, his small band of trusty companions and their battle to stop the Reapers destroying all intelligent life within the universe. I can't say much more as it would give away the plot and ruin it for those that have yet to play the games. Though I will say that about the last ten to fifteen minutes of the latest game has caused an uproar with the fans, myself included, and Bioware, the company who made the games, may even rework the ending http://blog.bioware.com/2012/03/21/4108/
I hope that this brings some enlightenment to you all. And no, I am not a 'spambot'.