You may be asked about the aspects of processes of inhalation and exhalation. 

Inhalation is breathing in
Exhalation is breathing out 

Inhalation

  1. Lungs move upward and outward
  2. Diaphragm contacts and flattens
  3. Intercostal muscles contract
  4. Ribs move upward and outward
  5. Volume inside thoracic cavity increases
  6. Pressure inside thoracic cavity decreases
  7. Air rushes into the lungs

Exhalation

  1. Lungs move downward and inward
  2. Diaphragm relaxes and curves upwards
  3. Intercostal muscles relax
  4. Ribs move downward and inward
  5. Volume inside thoracic cavity decreases
  6. Pressure inside thoracic cavity increases
  7. Air rushes out of the lungs

Concentration of each gas:

GasInhaled airExhaled air
Oxygen21%16%
Carbon dioxide0.03%4%
Nitrogen78%78%