Final answer:
The Milky Way is one of billions of galaxies, containing both visible and dark matter, and is a member of the Local Group. It has a supermassive black hole at its center and a mass largely made up of dark matter that exerts gravitational force. It is not the center of the universe nor does it contain most of the universe's mass.
Step-by-step explanation:
The Milky Way galaxy is one of billions of known galaxies in the universe. It is a member of an assembly known as the Local Group which spans about 3 million light-years and consists of 60 or so members, including three large spiral galaxies: our own Milky Way, the Andromeda galaxy, and M33. The Milky Way itself contains a thin disk with stars and interstellar matter, a halo with very old stars, a nuclear bulge, and a supermassive black hole at the center. While it has a visible component, much of its mass, including dark matter, exists as invisible matter extending far beyond the luminous stars. This matter emits no light and is only detectable through gravitational effects on visible matter. Our galaxy is not the central mass of the universe; rather, it is part of a vast cosmos filled with other galaxies, and does not contain most of the mass in the universe.