The Hubble Sequence, also known as the Hubble Tuning Fork, is a classification system for galaxies developed by astronomer Edwin Hubble. It categorizes galaxies into three main types: elliptical galaxies, spiral galaxies, and irregular galaxies. This system helps astronomers understand the structure and evolution of galaxies based on their shapes and characteristics. Elliptical galaxies are smooth and featureless, while spiral galaxies have distinct arms winding around a central bulge. Irregular galaxies lack a defined shape and often result from gravitational interactions. The Hubble Sequence provides a framework for studying galaxy formation and the dynamics of the universe.