A phase portrait is a graphical representation used in mathematics and physics to visualize the behavior of dynamical systems. It displays the trajectories of a system in a multi-dimensional space, where each axis represents a variable of the system. By plotting these trajectories, one can observe how the system evolves over time, revealing stable and unstable points. In a phase portrait, points correspond to the state of the system at a given time, while curves indicate the paths taken by the system as it changes. This tool is particularly useful in studying systems described by differential equations, such as those found in classical mechanics or population dynamics.