Abstract: Quantum communication has two main directions, one is quantum key distribution (QKD) which is to establish a quantum key for encrypting classical bits, the other is quantum teleportation which is to transmit quantum bits through quantum entanglement. We first introduce the BB84 protocol of QKD, the concept of quantum bits, the no-cloning theorem, quantum entanglement, and Bell's inequalities, then explain the principle of quantum teleportation. We also describe the experimental system of the "Mozi" satellite and the supporting ground stations, as well as the future development of wide-area quantum communication.