Can someone explain to me what this is, how it works, and some practical uses for it? I have looked everywhere online and haven't found anything useful. Just wanna know if it's useful or not.
A Color Ramp is used for many different things. You will use it all the time.
Here are a few examples.
It can be used to mix many different colors.
It can be used to control how much of a texture you see ie Roughness (and other inputs by clamping the white and blacks).
It can also be used as a mask to mix two materials together. By clamping down how much falloff or fade you want your texture/mask to have.
There are more use cases but here are some to get you started.