Everything is pretty much explained by the posts above mine. I just need to add, if you are running a node, decide which one you support, xt or core, and update accordingly. After and if you did that, relax and watch the show.

I just hope the show won't last too long since this block size debate has taken too long and has started hurting Bitcoin. This debate needs to end soon so we can move forward! I am for the bigger blocks by the way and have updated to the XT.