Different types of galaxies exist based on their shape such as elliptical, spiral, and irregular galaxies. Elliptical galaxies are smooth or oval, while spiral galaxies have a central bulge and spiral arms. Irregular galaxies do not have a defined shape. Galaxies form when large gas and dust clouds collapse under their own gravitational force, eventually producing stars. These stars then rotate around the center of the galaxy, and galaxies can merge to form larger ones