A Geiger counter is a device used to measure ionizing radiation, such as alpha, beta, and gamma rays. It consists of a Geiger-Müller tube that detects radiation particles and converts them into electrical pulses. These pulses are then counted and displayed, often in counts per minute (CPM), allowing users to assess radiation levels in their environment. Geiger counters are commonly used in various fields, including nuclear industry, medical applications, and environmental monitoring. They help ensure safety by detecting harmful radiation exposure, making them essential tools for professionals working with radioactive materials or in areas affected by radiation.