We perceive the Milky Way as a band or strip of light stretching across the night sky because of our vantage point within our galaxy. The Milky Way is a spiral galaxy, and we reside within one of its spiral arms, known as the Orion Arm or Local Spur.
When we look up at the night sky, we are gazing toward the plane of our galaxy, which is where the majority of stars, gas, and dust are concentrated. This plane is a flattened disk-like structure, and our position within it gives rise to the characteristic vertical appearance of the Milky Way.
Imagine you are standing in the middle of a flat field with tall grass surrounding you in all directions. When you look straight ahead, you will see the grass extending upward and appearing vertical. Similarly, the stars, star clusters, and interstellar dust that make up the Milky Way are spread out across the galactic plane. When we look toward the center of the galaxy from our position within it, the stars appear concentrated along a band that stretches across the sky, creating the vertical appearance of the Milky Way.
It's important to note that the specific appearance of the Milky Way can vary based on factors such as light pollution, atmospheric conditions, and the observer's location on Earth. In areas with minimal light pollution and clear skies, the Milky Way can be seen more prominently, with its band of light spanning across the sky.