B-lines (also called lung rockets or comet-tail lung artifacts) are bright, laser-like vertical artifacts that arise from the pleural line, extend to the bottom of the ultrasound screen without fading, and move synchronously with lung sliding. One or two B-lines per intercostal space is normal. Three or more B-lines per view (confluent B-lines) indicate interstitial syndrome — pulmonary edema, pneumonia, or interstitial lung disease. B-lines are one of the most useful findings in lung ultrasound and POCUS-guided fluid management.