The Copenhagen School refers to a group of physicists in the early 20th century who developed a foundational interpretation of quantum mechanics. Led by Niels Bohr, this school emphasized the importance of observation and measurement in understanding quantum phenomena, proposing that particles do not have definite properties until they are measured. This interpretation, known as the Copenhagen Interpretation, suggests that quantum systems exist in a superposition of states until observed. The school played a crucial role in shaping modern physics and laid the groundwork for future developments in quantum theory, influencing scientists like Werner Heisenberg and Erwin Schrödinger.