  Rotation is a key parameter in the evolution of stars. From 1 Myr (the age of
the ONC) to 4.5 Gyr (the age of the Sun), solar-like stars lose about 1-2
orders of specific angular momentum. The main agents for this rotational
braking are believed to be star-disk interaction and magnetically powered
stellar winds. Over the last decade, the observational fundament to probe the
stellar spindown has dramatically improved. Significant progress has been made
in exploring the underlying physical causes of the rotational braking.
Parameterized models combining the effects of star-disk interaction, winds, and
pre-main sequence contraction are able to reproduce the main features of the
rotational data for stars spanning more than 3 orders of magnitude in age. This
has allowed us to constrain stellar ages based on the rotation rates
('gyrochronology'). One main challenge for future work is to extend this type
of analysis to the substellar mass range, where the rotational database is
still sparse. More theoretical and observational work is required to explore
the physics of the braking processes, aiming to explain rotational evolution
from first principles. In this review for Cool Stars 15, I will summarize the
status quo and the recent developments in the field.
