A theory is a well-substantiated explanation of some aspect of the natural world, based on a body of evidence and reasoning. In science, theories are developed through the scientific method, which involves observation, experimentation, and validation. Examples include the Theory of Evolution and the Theory of Relativity, both of which have significantly advanced our understanding of biology and physics. Theories are essential for making predictions and guiding research. They help scientists and researchers to formulate hypotheses and design experiments. A robust theory can evolve over time as new evidence emerges, ensuring that our understanding of the universe remains dynamic and accurate.