  In this article we review the world-sheet scattering theory of strings on AdS
5 x S5. The asymptotic spectrum of this world-sheet theory contains both
fundamental particles and bound states of the latter. We explicitly derive the
S-matrix that describes scattering of arbitrary bound states. The key feature
that enables this derivation is the so-called Yangian symmetry which is related
to the centrally extended su(2|2) superalgebra. Subsequently, we study the
universal algebraic properties of the found S-matrix. As in many integrable
models, the S-matrix plays a key role in the determination of the energy
spectrum. In this context, we employ the Bethe ansatz approach to compute the
large volume energy spectrum of string bound states.
