Back in December, the Pokemon Bank was released in Japan... and very quickly taken back down due to problems Nintendo did not foresee with the application. Since then, fans have been eagerly awaiting the re-release of the Pokemon Bank, wanting to be able to have extra storage for their Pokemon and the ability to transfer Pokemon up from the Generation V games.
Pokemon Bank released again in Japan and Asia a couple weeks ago, and after the application was deemed stable, it was then released in Europe. Finally, yesterday Nintendo of America released the application in North America, finally making the application available worldwide.
If you have Pokemon X or Y, if you download the application between now and Marth 14th, you can try Pokemon Bank for a month for free; after that, the service will cost $5 a year. Also, if you download and use the Pokemon Bank, you can recieve a special Level 10 Celebi to transfer to your X or Y game.