Yeah it's pretty confusing for anyone who isn;t in the UK.
In the UK every year being No. 1 in the UK singles chart on the Sunday before Christmas makes you the Christmas No. 1. It's become a running thing over the years for people to try and battle for that spot, and often a lot of daft novelty songs top the charts on that week. You certainly don't get acts like Rage Against the Machine getting that No. 1 spot. For the last four years, the winner of The X-Factor (UK equivalent of American Idol) has released their debut song and easily obtained the Christmas No. 1 spot, making the whole thing rather pointless and one-sided. The X-Factor gets 10-20 million viewers here and a lot of media publicity hence why a No. 1 song is almost inevitable. This year some people on Facebook set up a group and started a campaign for people to download Killing in the Name by Rage Against the Machine and make that Christmas No. 1 instead. Last year there was an unsuccessful attempt to get Hallelujah by Jeff Buckey to No. 1 for Christmas. The group for RATM wound up getting over 900,000 members, the whole thing snowballed (even the band got involved a bit) and got lots of publicity, and today it was confirmed that Rage Against the Machine had got the Christmas No. 1 spot. Which was a bit of a surprise really.