We discuss the use of quantum algorithms in three areas: cryptography, computations, and communication. We discuss three aspects: how quantum algorithms can help, the problems for which they can help, and the problems for which they offer no benefits. We give examples of all cases. We discuss which existing crypto-systems are vulnerable or resilient against quantum attacks. We give examples of collaborative communication tasks where quantum communication helps. We conclude by characterizing which tasks and problems are currently believed to be aided by quantum computers.