The F-layer, also known as the F region, is a part of the Earth's ionosphere, located approximately 150 to 1,000 kilometers above the surface. It is characterized by a high concentration of free electrons and ions, which are created by solar radiation. This layer plays a crucial role in radio wave propagation, allowing long-distance communication by reflecting certain frequencies back to the Earth's surface. The F-layer is divided into two sub-layers: the F1 and F2 layers, with the F2 layer being more prominent during the day. The behavior of the F-layer can be influenced by solar activity, such as solar flares and sunspots, which can enhance its ionization levels. Understanding the F-layer is essential for improving technologies like GPS and satellite communications.