Gait is inherent to human life and hence its importance is often overlooked. But walking remains the most basic form of transportation and almost all journeys begin and end with a walk, regardless of the modes used in-between. Gaining a good understanding of pedestrian's dynamics is thus a crucial step in meeting the mobility and accessibility needs of people by providing safe and quick walking flows. This paper presents a critical and integrative review of research on pedestrian's dynamics and associated topics. The review focuses on comprehensive theories and models, with an emphasis on the advances made possible by the application of the constructal law. Constructal law points out that the emergence and evolution of design in pedestrian dynamics is analogous to that of animate flow systems. Most importantly, it also highlights that the basic features of pedestrian dynamics and supportive walking infrastructures can be optimally envisaged with the help of a few fundamental physics laws.