Say you want to freeze the randomly generated trees you've made. Typically, when using a random node from UE4's artillery, this information will be lost once you exit the game. With RandomStream, you can actually save the seed that generated the random output and load the same random output by calling on this seed. So in UE4, you will find a blueprint node called Make RandomStream. This node has one input pin called Initial Seed.

The reason we use a seed is because this is a pseudo random-number generator. This means that the numbers are calculated and are deterministic. Pseudo means that we will use algorithms to calculate the randomness; however, by calculating the randomness, we technically know what it will be beforehand, thus making it deterministic. The contrast is true randomness, which captures noise from a forest, waterfalls, the atmosphere, or even a TV channel. The reason this will be indefinitely more random is that the noise captured is unlikely...