system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How a computer randomly generates something

How does a computer randomly generate something, ie Reddit's RANDOM link up top. How does the site select the "random" link?
gpt
Computers have no imagination, they just do maths.  This means they can't make up random numbers but they can take existing numbers and come up with new ones.  When you generate a bunch of numbers from an existing one, that one is called a 'seed'.  The same seed will usually always result in the same bunch of new numbers.  
This means the trick is coming up with unexpected seeds.  One way to do that is to check the system time (the little clock in your computer) but that's pretty predictable too.  A better way to do that is to tell the computer to come up with seeds based on how the user is interacting with the computer.  This is a good way because the computer can't predict when you're going to hit a key or click the mouse and it's practically impossible for other people to duplicate your timing.