This tag is for questions dealing with random numbers, pseudorandom numbers, and computer entropy.
In computing a "random" number is used for a variety of purposes including:
Generating cryptography keys such that two pieces of data are highly unlikely to be encrypted with the same key.
Allowing AI some measure of unpredictability: an enemy character in a game, for example, might react slightly differently on two different playthroughs, making the game more difficult.
Most computers are really good at generating pseudorandom numbers: these are numbers that typically start from a seed value, and generate a sequence of numbers that repeats after many values are generated. One may "reseed" the pseudorandom number generator to generate the same sequence again.
Another way of generating randomness is through entropy: a source of data outside of the computer's core CPU and memory is used to generate a sequence of bits. Perhaps tiny fluctuations in the case temperature, variations in the input voltage of the power supply, or some other source of data could be used to generate bits that are more unpredictable than a pseudorandom number generator (but may still have bias).
Questions in this tag will deal with how to generate or use random numbers in computing.