Further reading
To read more about what each shader node does, you can refer to the official documentation at the following link: https://docs.blender.org/manual/en/2.93/render/shader_nodes/.
For further practice, imagine where else the method for the lava texture could be used. Perhaps, with carefully planned values and more color variations, the hot lava might be rust, and the cool lava might be paint?
If you are curious and would like to investigate different software out there capable of producing procedural textures, you can give Adobe Substance Designer a try. It’s a powerful program dedicated solely to creating textures. Not all of the nodes are labeled the same, but there are a lot of similar nodes to Blender’s. In fact, if you practice your skills there and look at other people’s creations, you might gain insight into creating such textures in Blender.