Pseudo-random
Numbers from a fixed recipe that look random but repeat exactly from the same seed.
See it in Cellular automata. Press Random to fill the grid, then Play to watch what grows from it.
In plain words
A computer follows exact steps, so it cannot roll real dice. Instead it uses a recipe that turns one number into a long run of numbers that look random. The starting number is called the seed. Start from the same seed and you get the very same run, every time. That is useful: a pattern you like can be made again exactly.