Capture the Tag is a local competition, sort of like a treasure hunt. With $15000 in prizes it sounds like something well worth the effort to participate in.
Basically you hunt around town with your smart-phone making sure you have the Microsoft Tag app. You find the Tags which lead you to clues. That is it in a nutshell. It is a great idea and hopefully creates some buzz for local businesses!
See the Capture the Tag Web site for more details and the rules.