What does it mean to be ``random''? What matters to most of these problems
is that there is a sequence of numbers *with no observable patterns*.
One could generate such a sequence by looking at radioactive decay or something,
but on a computer one usually generates a new random number from the old
one (no randomness at all!) One starts these random number generators
with a *seed*: if you don't change the seed, you get exactly the
same random numbers every time!

Statistical Mechanics: Entropy, Order Parameters, and Complexity, now available at Oxford University Press (USA, Europe).