This text is part of a volume entitled " Quantum information - an introduction to basic theoretical concepts and experiments", to be published in Springer Tracts in Modern Physics. In this article I will give an account of the basic concepts of Quantum Information Theory, staying as much as possible in the area of general agreement. So in order to enter this new field, plain quantum mechanics is enough, and no new, perhaps obscure, views are needed. There is, of course, a characteristic shift in emphasis expressed by the word "information", and we will have to explore the consequences of this shift.