An interactive 3D visualization of perlin noise made with Javascript and HTML (P5*js)
Play with it here.
Perlin noise is a type of gradient noise, in order to create a random landscape we need some random values for the z axis, but a totally random function is not enough. Perlin noise has a smooth transition between values, they are connected. Here we can see a 2D image of Perlin noise.
The z axis is actually moving though a plane like this, using these values to create the landscape.