This review paper by Codling, Plank, and Benhamou aims to introduce the mathematics behind random walks and explain how these models can be used to understand biological processes. The authors cover the fundamental theory of random walks, including simple isotropic random walks (SRW), correlated random walks (CRW), and biased random walks (BRW). They discuss the mathematical theory behind SRW, its relation to Brownian motion, and how it can be extended to include drift and waiting times. The paper also explores the use of random walk models in two main biological contexts: the movement and dispersal of animals and micro-organisms, and chemotaxis models of cell signaling and movement. The authors provide detailed derivations and explanations of the governing equations for these models, such as the drift-diffusion equation and the telegraph equation. They also discuss the limitations of the models and the connections between different types of random walk models. The paper includes examples and figures to illustrate the concepts and provides a comprehensive reference for both mathematicians and biologists.This review paper by Codling, Plank, and Benhamou aims to introduce the mathematics behind random walks and explain how these models can be used to understand biological processes. The authors cover the fundamental theory of random walks, including simple isotropic random walks (SRW), correlated random walks (CRW), and biased random walks (BRW). They discuss the mathematical theory behind SRW, its relation to Brownian motion, and how it can be extended to include drift and waiting times. The paper also explores the use of random walk models in two main biological contexts: the movement and dispersal of animals and micro-organisms, and chemotaxis models of cell signaling and movement. The authors provide detailed derivations and explanations of the governing equations for these models, such as the drift-diffusion equation and the telegraph equation. They also discuss the limitations of the models and the connections between different types of random walk models. The paper includes examples and figures to illustrate the concepts and provides a comprehensive reference for both mathematicians and biologists.