Milky Waygalaxy. It is named for the very bright band of stars that are best seen in the Southern Hemisphere. From there, you are looking at the bright centre of the galaxy. In the Northern Hemisphere you are seeing its edge. Since Sol and Earth are about three quarters of the way to the edge, and since there are few stars at the edge, it is a very big difference in brightness.
A galaxy is a big group of millions of stars that all orbit around their galatic centre, like planets orbit a star. It takes millions of years for a star to go all the way around the galaxy.
These cycles are important because different areas of the galaxy have more asteroids, which become meteors if they hit the Earth's atmosphere. Very large ones can do horrible damage - many scientists believe dinosaurs were made extinct by an asteroid that hit Earth about 60 million years ago. About every 30 million years, astronomers believe, Sol and Earth go through a part of the galaxy that has more asteroids. At this time there is great danger. This is supposed to be coming up soon, either right now or in million years (nobody really knows) - but certainly before five million years.
There are millions of other galaxies visible in the universe. It is hard to say if those we see, are all that there really are. It is even hard to say if "are" means anything if we can never see or measure them. Models of our universe are sometimes finite, and sometimes infinite - if they are infinite we can never see all the galaxies.
Another way the Milky Way has affected things is by astrology. The Inca Empire was created in less than a hundred years because its founders believed that, when the Milky Way moved to a certain point in the sky by stellar precession, time would end. They wanted to be ready. That time was almost exactly when Spain invaded. The Inca did not fight because they believed the Spaniards to be divine justice. Their empire was destroyed and became part of what is now Peru.