The act of generating a sequence of numbers or symbols randomly, or (almost always) pseudo-randomly; i.e., with lack of any predictability or pattern.
Random generation, or random number generation is the use of mechanical or electronic devices or more usually algorithms to produce a sequence of numbers which lack any predictability or regularities, generally according to some particular probability distribution over the numbers or symbols, often equiprobably (when this makes sense). These values are used to approximate expectations, validate models, or to reproduce random experiments. Most random generators are pseudo-random in that they produce a deterministic sequence that can be repeated by using the "seed" the generators are initialised with.
Reference: http://en.wikipedia.org/wiki/Random_number_generation