  General relativity marked the beginning of modern cosmology and it has since
been at the centre of many of the key developments in this field. In the
present review, we discuss the general-relativistic dynamics and perturbations
of the standard cosmological model, the Friedmann-Lemaitre universe, and how
these can explain and predict the properties of the observable universe. Our
aim is to provide an overview of the progress made in several major research
areas, such as linear and non-linear cosmological perturbations, large-scale
structure formation and the physics of the cosmic microwave background
radiation, in view of current and upcoming observations. We do this by using a
single formalism throughout the review, the 1+3 covariant approach to
cosmology, which allows for a uniform and balanced presentation of technical
information and physical insight.
