system
Given the following post, respond as if you're commenting on Reddit:
human
How can computers generate random numbers?
gpt
Generally what you think of as a random number is actually what is called a "psuedo-random number".  What this means is that the number isn't really random, but that you should be unable to guess what the next number is simply by seeing what number it has given you in the past.  Even with something like this though, you need an original random number (called a "seed") to start off the pseudo-random number generator.  To get a seed, your computer might measure something that seems random enough (like the amount of time in between your keystrokes, or the amount of time in between requests from the internet). 

For things that need *true* random numbers (like some internet security things) they will often use an outside source of data that should be random, and hook that up to a computer (like a geiger counter measuring radiation, or a something sampling weather data).