The Earth's atmosphere is categorized into four distinct layers, each with unique characteristics and functions. These layers are the troposphere, stratosphere, mesosphere, and ionosphere, which is frequently referred to as the thermosphere in modern terminology. This classification helps scientists study and understand the atmospheric conditions and phenomena that occur at various altitudes.

By dividing the atmosphere into these layers, researchers can better analyze weather patterns, climate change, and other atmospheric processes. The troposphere is where most weather events happen, while the stratosphere contains the ozone layer. The mesosphere and ionosphere play significant roles in satellite communication and space exploration, making this division essential for both scientific research and practical applications.