In recent years, lung ultrasonography has acquired an important role as a valuable diagnostic tool in clinical practice. The lung is usually poorly explorable, but it provides more acoustic information in pathological conditions that modify the relationship between air, water and tissues. The different acoustic impedance of all these components makes the chest wall a powerful ultrasound reflector: this is responsible for the creation of several artifacts providing valuable information about lung pathophysiology. Lung ultrasonography helps in the diagnostic process of parenchymal and pleural pathologies, in the differential diagnosis of dyspnea and in the clinical and prognostic evaluation of the SARS-CoV-2 infection.