Its just maps that are out for the pc version.
You already said that

I don't have the PC version, I will get the new maps on XBLA.
Its just maps that are out for the pc version.
1up said:Portal: Still Alive. Essentially an expansion for the original game, Still Alive will feature new stages and Achievements, and be available exclusively on Xbox Live Arcade this fall. GLaDOS tells us the Enrichment Center has been hard at work, which should at least keep us satisfied until Portal 2 comes next year.