Effective field theory is a theoretical framework used in physics to describe the behavior of systems at a particular energy scale or distance scale without needing to take into account all the details of the underlying microscopic theory. It allows scientists to simplify complex physical systems by focusing on the most important interactions and phenomena that are relevant for a particular scale of interest. Effective field theory has been successfully applied in various areas of physics, including particle physics, condensed matter physics, and cosmology. It provides a powerful tool for making predictions and interpreting experimental results in a wide range of physical systems.