A path in the sky
On calm nights we can see a white stripe that crosses the sky from side to side, with many stars.
They are only a small part of our neighbors. Together we form the milky way, our galaxy. The Romans called it "Way of milk", which is what is meant in latin via lactea.
The milky way is our Galaxy
The Solar system is in one of the spiral arms, about 30,000 years light from the Center and about 20,000 of the end.
The dairy is Via a large Galaxy, spiral and may have about 100 billion stars, including the Sun. In total about 100,000 light-years in diameter wide and has a mass of more than two trillion times that of the Sun.
Every 225 million years ago the Solar system complete a rotation around the center of the Galaxy. It moves some 270 km. per second.
We can not see the bright Center opaque materials, cosmic dust and cold gases, which do not let light stand. It is believed to contain a powerful black hole.
The milky way has a convex lens. The kernel has a central area of ellipse-shaped and about 8,000 light-years in diameter. The stars of the core are more clustered than the arms. To its surroundings there is a cloud of hydrogen, some stars and star clusters.
The milky way is part of the Local Group
Together with galaxies of Andromeda (M31) and the triangle (M33), clouds of Magellan (satellites of the Milky Way), galaxies M32 and M110 (satellite of Andromeda), galaxies and smaller nebulae and other minor systems, form a group bound by gravity.
In total, there are about 30 galaxies that occupy an area of about 4 million years diameter light in the Local Group.
All group orbit around the large cluster of galaxies in Virgo, about 50 million light years.