This book highlights the basic information about lightning. It is an unpredictable disaster, and it is an extremely complex electrical discharge phenomenon. A complete theory of lightning does not exist till now. This book elaborates on the basic formation of lightning, terminologies related to lightning, and the preliminary lightning theory. There are different types of lightning, such as cloud flashes, ground flashes (both positive and negative), and air discharges. This book explains some unusual events related to lightning and inspects innovation. This book also describes the measurement of electric and magnetic fields generated by lightning, which are the basic parameters for lightning fundamentals.