They get new chromosomes that are a combination of the two corresponding chromosomes from the father (or mother). The exact points in each chromosome where the crossovers happens are different (perhaps almost random), so each one of the sperms (eggs) is a very different unique snowflake.
(And there are also a few mutations that make them slightly more unique.)
http://en.wikipedia.org/wiki/Chromosomal_crossover
They get new chromosomes that are a combination of the two corresponding chromosomes from the father (or mother). The exact points in each chromosome where the crossovers happens are different (perhaps almost random), so each one of the sperms (eggs) is a very different unique snowflake.
(And there are also a few mutations that make them slightly more unique.)