Can Computers Generate Random Numbers?

Computers can generate truly random numbers by observing some outside data, like mouse movements or fan noise, which is not predictable, and creating data from it. This is known as entropy. Other times, they generate “pseudorandom” numbers by using an algorithm so the results appear random, even though they aren't.

Why is it difficult to generate truly random numbers on a computer?

A cryptographically secure random number generator is going to take some external source of entropy to make the device non-deterministic. That is why it is impossible to get a truly random number.

Can humans generate random numbers?

Nothing can generate random numbers. There always has to be something, or some reason to everything. Even computer random generation algorithms have a seed, i.e., the number starting from which the random generation algorithm is executed. So, humans are incapable of producing a random number.