The respiratory system consists of respiratory passages and organs that bring atmospheric (external) air into the body. There are also auxiliary structures that support breathing, namely: muscles (diaphragm, intercostals, etc.), ribs, cartilages, etc. Breathing, is a physiological process that takes place in two unequal but connected parts. Part at the cellular level and part at the level of the respiratory system. Cellular respiration, which takes place in the mitochondria, is the process by which the energy necessary for metabolic processes is generated. External respiration takes place in two parts, i.e. phases: active phase, i.e. inspiration (inhalation) and passive phase, i.e. expiration (exhalation). Spirometry is a key diagnostic method that helps to understand lung function and provides important information for the diagnosis and management of lung diseases. The respiratory system plays a key role in supporting physical activity by enabling an adequate supply of oxygen to the body. Physical activity is of great importance for the respiratory system. It improves its function and adapts it to greater needs during physical exertion. Different sports can have different effects on lung functions, depending on their nature and intensity. However, sports that require prolonged aerobic activity are often considered the most beneficial for improving lung capacity and overall lung function. This paper describes the respiratory system and its function, as well as the influence of physical activity on this system.