It seems, off the top of our heads, like Samsung took the Galaxy S and added a few "advanced" features. For one, RAM has been increased from 512MB to 768MB. It has a dual core 1.0 GHz processor vs. the original Galaxy S' single core 1 GHz processor. It also adds HSPA 14.4Mbps connectivity vs. the original's 7.2Mbps data speed.
Samsung said it plans to begin a gradual roll out of the Galaxy S Advance in Russia next month. It will follow that with Europe, Africa, Middle East, Southeast and Southwest Asia, Latin America and China. If you notice that the U.S. is absent from that list, you'd be right.