Short answers, pulled from the story.
The Milky Way is a collective illusion created by billions of distant stars that appears as a hazy band of light arching across the night sky. This visual phenomenon is visible to the naked eye as a dim, unresolved glow resulting from countless stars in the galaxy's spiral arms that are too far away to be individually distinguished from Earth.
Galileo Galilei pointed his telescope at the band on the 2nd of November 1610 and shattered the illusion that the Milky Way was a cloud or river of milk. His observation revealed that the Milky Way was composed of a vast multitude of faint stars rather than a byproduct of the Earth's atmosphere as philosophers like Aristotle had believed.
Edwin Hubble used the Mount Wilson Observatory's Hooker telescope to resolve the outer parts of the Andromeda Nebula into individual stars and found it to be 275,000 parsecs from the Sun. This discovery proved that the Milky Way was just one of many galaxies and expanded the known universe by orders of magnitude.
Dark matter comprises 90% of the total mass of the Milky Way, which is estimated to be between 5.8 and 1.29 trillion solar masses. The existence of this dark matter is supported by the flat rotation curve of the galaxy, which suggests the presence of a massive, unseen halo extending beyond one hundred kiloparsecs from the Galactic Center.
The Milky Way began as one or several small overdensities in the mass distribution in the Universe shortly after the Big Bang 13.61 billion years ago. The age of the galaxy is estimated to be at least 12.6 billion years, with some stars such as 2MASS J18082002-5104378 B being 13.5 billion years old.
The name Milky Way is derived from the Classical Latin via lactea and the Greek galaxias, meaning milky circle. In Greek mythology, the Milky Way was formed when Hera, the goddess of marriage, pushed the infant Heracles from her breast, causing her milk to spill across the sky.