HighlightsWhat are the main findings?There has been remarkable growth in lung ultrasound publications over the last decade. Given the large amount of new data available on this topic, a practical clinical review summarizing the most recent findings in this matter could help the physicians gain confidence in performing the technique.Following the recent ESICM consensus statement on critical care ultrasound, questions have been raised regarding the definitions of different skill levels. There are no clear criteria for differentiating basic skills from intermediate or advanced. In addition, the training path remains unclear.What is the implication of the main finding?A practical, up-to-date approach to lung ultrasound in intensive care units and emergency departments. Supplemented by diagnostic and interventional flowcharts to guide its clinical application in everyday practice based on common clinical scenarios.In order to categorize the different levels of skill in lung ultrasound, we propose a new four-level classification which aims to describe, from basic to expert, the various competence that can be achieved.AbstractLung ultrasound has become a part of the daily examination of physicians working in intensive, sub-intensive, and general medical wards. The easy access to hand-held ultrasound machines in wards where they were not available in the past facilitated the widespread use of ultrasound, both for clinical examination and as a guide to procedures; among point-of-care ultrasound techniques, the lung ultrasound saw the greatest spread in the last decade. The COVID-19 pandemic has given a boost to the use of ultrasound since it allows to obtain a wide range of clinical information with a bedside, not harmful, repeatable examination that is reliable. This led to the remarkable growth of publications on lung ultrasounds. The first part of this narrative review aims to discuss basic aspects of lung ultrasounds, from the machine setting, probe choice, and standard examination to signs and semiotics for qualitative and quantitative lung ultrasound interpretation. The second part focuses on how to use lung ultrasound to answer specific clinical questions in critical care units and in emergency departments.