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This should answer your questions. Usually the version differences are version-exclusive Pokémon; Black has Gothita where White doesn't, but White gets Solosis. Things like that.
Honestly there's lots of ways they're different. Move tutors, different storyline, some new characters, set in a different time period to these games, and so on. Soon other than the link Cyclone provided, you can also read about it in the eventual Black 2 and White 2 FAQ which'll hopefully be very comprehensive! Ask in Quick Questions of either section next time though please. :)