The PS Vita does not use UMDs. Instead, it uses cartridges and digital downloads. The UMD is going extinct, putting current PSP owners in a bind should they want to play their PSP titles on the Vita.
Today, Sony announced its solution: UMD Passport.
Starting December 6, the UMD Passport service will start in Japan. Here's how it works: Download a free app called "UMD Registration Application". After that, enter your UMD game disc into your PSP, and according to the on-screen prompts, register your UMD via your PSN Account. The UMD will then be available for purchase.
Once the PS Vita is released in Japan on December 17, you can then download the title on your new Sony handheld. According to Sony, the games will be available at an "agreeable price".
Currently, 40 game companies are offering 200 UMD titles as part of Sony's UMD Passport program. The digital versions of the games are priced anywhere between ¥100 ($US1.29) to ¥2400 ($US31).