What is Gradient Descent?

This tutorial is on the basics of gradient descent. It is also a continuation of the Intro to Machine Learning post, "What is Machine Learning?", which can be found here. Gradient descent is a method of finding the optimal weights for a model. We use the gradient descent algorithm to find the best machine learning model, with the lowest error and highest accuracy. A common explanation of gradient descent is the idea of standing on an uneven baseball field, blindfolded, and you want to find the lowest point of the field.