Elon Musk believes that AI poses a fundamental risk to human civilization. The document then provides explanations of different types of AI like artificial neural networks, convolutional neural networks, recurrent neural networks, supervised learning, unsupervised learning, and reinforcement learning. It gives examples of applications for each type and compares human intelligence and learning to AI systems. In the end, the document asks if AI is really a threat to humans according to the definition of AI provided.