A quantum communication channel can be put to many uses: it can transmit
classical information, private classical information, or quantum information.
It can be used alone, with shared entanglement, or together with other
channels. For each of these settings there is a capacity that quantifies a
channel's fundamental potential for communication. In this introductory
talk, I will discuss what we known about the various capacities of a quantum
channel, including a discussion of synergies between different channels and
related additivity questions.