Point-of-care ultrasound (POCUS) is rapidly advancing in clinical medicine, with applications growing across many specialties. A solid understanding of ultrasound physics helps clinicians who utilize POCUS to properly capture, refine, and interpret images to improve patient care. This chapter explores key topics like the basics of knobology, ultrasound wave properties, types of probes including silicon chip probes and their operation, factors that impact image resolution, and different ultrasound modes. We will also discuss image artifacts, the Doppler shift, and its clinical uses. Lastly, we will cover ultrasound safety and emphasize the ALARA principle (as low as reasonably achievable) to minimize risks. A practical understanding of these core concepts forms the foundation for effective and reliable use of POCUS at the bedside.