A random number generator (RNG) is a pseudo-random number generator. It is a tool used for generating a sequence of numbers that have a property of randomness, i.e. each number in the sequence is independent of the others and thus also from the preceding and following numbers. Such a sequence is suitable for the generation of a large amount of random numbers in practice.

To have a good chance of getting a random number, the RNG should be unpredictable and not repeatable. It should not be predictable. However, the sequence generated by the RNG is not necessarily a series of random numbers. Therefore, it is important to have a way to distinguish a truly random sequence from a series that is not truly random. A random number generator based on physical phenomena is called a true random number generator, or TRNG. Such a generator is based on phenomena that are not subject to human control and thus, the sequence generated by such a generator is truly random.

The generation of random numbers in real world scenarios is not an easy task. For example, you need a physical object to generate the random num to make dice rollers. If you use a computer, you can use a TRNG, which generates the sequence of numbers using the properties of a physical phenomena such as thermal noise or other quantum phenomena. A TRNG should not be confused with a pseudo-random number generator. The former does not generate numbers from a limited number of possibilities while the latter does. A pseudo-random number generator is based on mathematical properties, and is thus, easier to generate a sequence of numbers.