Gradient descent is a widely used optimization algorithm in machine learning aimed at minimizing an objective function, often referred to as a loss function, which measures the error between predictions and actual outcomes. The algorithm starts with randomly initialized parameters and iteratively adjusts them by taking steps proportional to the negative of the gradient, which indicates the slope or direction to move for error reduction. The learning rate, denoted by alpha, is crucial in determining the step size; it must be optimally set to ensure convergence without overshooting the minimum. While gradient descent is efficient, especially for convex functions, adaptations are necessary for different scenarios, such as handling large datasets or non-convex functions typical in deep learning.