Terminator Salvation

I am one of the lucky bloggers invited by TV 5 to watch Terminator Salvation.I am not a Terminator fan so I really can`t relate with the elements present in this movie.But I was amazed with the super high tech robots and gadgets here.All I can say is When Arnold Schwarzenneger specially appeared the crowd was cheering.The only moment I hear them scream . I cannot distinguish which part is the past,which is the present.Why are they fighting? What is the role of the child? I really can`t understand everything.