Layer 1: Troposphere
The lowermost of the atmosphere, in contact with the ground is called the troposphere. Temperature decreases with altitude in the troposphere.
We live and breathe in the troposphere, which extends from the ground to about 10 km elevation. What you see from an airplane window is the troposphere.
80% of the mass of the atmosphere is in the troposphere, as the weight of the overlying atmospheric layers compresses the air near the ground.
Most weather is confined to the troposphere as well (although some cumulonibmus clouds reach the stratosphere).