This chapter introduces the neural network, which is widely used as the model for Machine Learning. The neural network has a long history of development and a vast amount of achievement from research works. There are many books available that purely focus on the neural network. Along with the recent growth in interest for Deep Learning, the importance of the neural network has increased significantly as well. We will briefly review the relevant and practical techniques to better understand Deep Learning. For those who are new to the concept of the neural network, we start with the fundamentals.