The ionosphere is a region of Earth's atmosphere, located approximately 30 miles to 600 miles above the surface. It contains several layers, primarily the D layer, E layer, and F layer, which are formed by the ionization of gases due to solar radiation. These layers play a crucial role in radio wave propagation, reflecting and refracting signals back to Earth. The D layer is the lowest and absorbs high-frequency radio waves during the day, while the E layer can reflect medium-frequency waves. The F layer, which is the highest, is split into F1 and F2 layers at times and is essential for long-distance communication, especially at night when it becomes more ionized.