  We review the recent progress in the understanding of the relaxation of
isolated near-integrable quantum many-body systems. Focusing on
prethermalization and universal dynamics following a quench, we describe the
experiments with ultracold atomic gases that illustrate these phenomena and
summarize the essential theoretical concepts employed to interpret them. Our
discussion highlights the key topics that link the different approaches to this
interdisciplinary field, including the generalized Gibbs ensemble, non-thermal
fixed points, critical slowing and universal scaling. Finally, we point to new
experimental challenges demonstrating these fundamental features of many-body
quantum systems out of equilibrium.
