Radiation is electromagnetic energy which is a source and travels through space at the speed of light. This energy has an electric field and a magnetic field, and they can cause the ionization of gases which behave as waves as well as particles. This is called radiation “electromagnetic waves”. Electromagnetic radiation is like Visible light. They can produce other chemicals and biological changes mainly by ionization and excitation. Radiation with the highest energy includes ultraviolet radiation, x-rays, and gamma rays. When they interact with atoms they can remove electrons and cause the atom to become ionized. Radioactivity material also produced radiation from an unstable atom to get a more stable state called Radionuclide. X-rays and nuclear medicine both are using ionizing radiation. In x- rays images are produced by absorption of X-rays in the human body, but in nuclear medicine, images are obtained by mapping the distribution of radioactivity within the patient body. To define actual measurements of radiation, we use different types of radiation measurement devices like as GM counter, film badge, TLD, Pocket dosi- meter etc. The radiation protection device determined the actual types of radiation and the correct calculation of the radiation. Many types of the radiation are present in our environment like ionizing and non-ionizing. When we are working in the radiation area, we will take care of the Radiation dose amount to avoid the late and earlier side effects of the radiation. All Radiation workers follow ALARA and KERMA principles to avoid reducing radiation doses. The ALARA principle defines patient protection as well as personnel protection by following the Time, Distance, and Shielding. According to ALARA, the radiation is measured in Gray (Gy) or Sievert (Sv), which are international units. The radiation personal dose is measured by TLD badges in hospitals, Diagnostic centers, and any kind of radiation area. The radiation dose should not exceed 100 mSv in 5 years and in one-year maximum dose is 30 mSv. Ionizing radiation helps in cancer treatment. Radiotherapy treated all types of cancer, tumors, and any pathological changes with the help of radiotherapy, teletherapy, and brachytherapy.