I see minecraft seeds listed, and I started trying some of my own.

I have noticed using the same seed produces very similar styles of maps, i.e. start in a specific biome, very high mountains etc, but do they reproduce the maps exactly and you just spawn in the same place, or are they just a very specific set of rules for the area you first spawn?

If I have two maps of the same seed, and I walk 1000 blocks north, will the maps be identical/similar or totally random after the first spawn area?