In order to protect and secure the sensitive data over the internet, the current data security methods typically depend on the cryptographic systems. Recent achievements in quantum computing is a major challenge to such cryptography systems. In this way, the quantum key distribution (QKD) technique evolves as a very important technique which gives un-conditional data security. This technique is based on the laws of quantum physics for its security. This article gives a detailed description of the QKD technique. This technique secures the encryption key delivery between the two authenticated parties from the unauthorized access. In the next phase, quantum cryptography model is discussed. Finally, some important application areas and limitations of this technology are be discussed.