A Theoretical Physicist is a scientist who uses mathematical models and abstractions to explain and predict natural phenomena. They often work on concepts that may not yet be observable, such as black holes or string theory, pushing the boundaries of our understanding of the universe. These physicists play a crucial role in advancing knowledge in areas like cosmology and particle physics. By developing theories that can later be tested through experiments, they help bridge the gap between theoretical predictions and empirical evidence, contributing significantly to the scientific community's understanding of the fundamental laws of nature.