Welcome to Your Daily Nerd Thing. At the most recent Blizzcon the new World of Warcarft expansion was announced Battle for Azeroth. This week Blizzard made the preorder available and that everyone who preorder would get early access to the new allied races that will be introduced. A lot of people were eager to get in on that early. In fact so many people were that for several hours the Blizzard shop and World of Warcraft itself were not working.
The game is functioning properly now and I have not heard of any more problems with the online shop. But you still might want to wait a day or two just in case.
I had mixed feelings about the announcement of Battle for Azeroth that I will have to get into some other time. But I was very interested in the new allied races. And it looks like the initial ones they announced will not be the only ones. There is plenty of wild speculation about what other allies races will show up and what the requirements to unlock them will be.