Random number
A random number is a number selected from a known set of numbers in such a way that each number in the set has the same probability of occurrence.For true randomness random numbers must be indepenently generated, so that there are no patterns. Numbers generated by the roll of a dice or a toss of a coin usually have a strong random element, however they are cumbersome, and so various solutions exist for generating large numbers of 'random' numbers quickly.
The most simple of these are tables of random numbers, that were generated by hand, or more frequently by a hardware random number generator. Hardware random number generators usually rely on some physical effects that are non-predictable, like the timing of background radiation events.
Also, in computing there are pseudo-random number generator, in which an algorithm is used to generate a sequence that looks like a random number sequence. However, if the sequence is used to generate enough numbers, a pattern can be spotted.