A positron is a subatomic particle that has the same mass as an electron but carries a positive electric charge. It is considered the antimatter counterpart of the electron. When a positron encounters an electron, they can annihilate each other, producing gamma-ray photons in the process. This phenomenon is a key aspect of particle physics and helps scientists understand the fundamental forces of the universe. Positrons are used in various applications, most notably in positron emission tomography (PET) scans, a medical imaging technique. In PET scans, a radioactive substance that emits positrons is introduced into the body, allowing doctors to visualize metabolic processes and detect diseases like cancer.