Make sure to import the Extended math support and Noise generator extensions into your project. Read this to learn how to import extensions.
What is Procedural Generation
Procedural generation is way for the computer to create parts of the game for you, typically this means textures or terrain. A good example of procedural generation is Minecraft where every world created is unique, but made up of the same elements; dirt, stone, water, etc.
Understanding procedural generation explains why things happen and implementing procedural generation explains how it happens
Articles about Procedural Generation: