Galactic structure refers to the organization and arrangement of stars, gas, dust, and dark matter within a galaxy. Most galaxies, including our own Milky Way, have a central bulge surrounded by a flat disk containing spiral arms. These arms are where most of the galaxy's young stars and nebulae are found, while the central bulge typically contains older stars. In addition to the disk and bulge, galaxies also have a halo of dark matter and older stars that extends beyond the visible components. The structure of a galaxy can vary significantly, leading to different types, such as spiral, elliptical, and irregular galaxies, each with unique characteristics and formations.