According to Landauer, "information is physical". The most obvious consequences of this fact are of limiting nature: Thermodynamics puts limitations on the smallness of computing devices as well on the reachable computation speed. These issues are discussed as an introduction. Fortunately, the laws of physics also allow for more efficient of more secure information processing, when they are used in the right way. In quantum information, we are interested in the consequences and the possibilites offered by the laws of quantum physics for all kinds of information treatment. Followed by an introduction to the basic principles of quantum physics, such as superposition, interference, or entanglement, a variety of subjects are treated: Quantum algorithms for integer factoring or search in an unsorted database, quantum teleportation, superdense coding, quantum communication complexity and "pseudo-telepathy," quantum cryptography, as well as the main notions of quantum information theory such as quantum coding.