"A few days ago, something unsettling happened, and unless you follow a ton of indie game developers on Twitter like I do, you may have missed it. XNA is dead.
Allow me to backpedal ever so slightly, so I can explain that question you’re probably having as “What the hell is XNA?” XNA is a programming language used on Xbox Live Arcade and Xbox Live Arcade Games. It has been used for games outside of ones on XBLIG, such as Terraria, Sol Survivor, and Magicka. It is also exclusive to Microsoft products, which is why Terraria was on PC as well." - Frank Falcone of Geekenstein.com