According to David A. Kolb, learning is a four-step process that involves concrete learning, reflective observation, abstract conceptualization, and active experimentation. This four-stage cycle is based on John Dewey and Kurt Lewin's ideas of experiential and active learning. Kolb's theory also includes four distinct learning styles and highlights the ongoing nature of learning. The cycle can be entered at any stage and emphasizes the role of experience, reflection, conceptualization, and experimentation in the learning process.