  Magnetars are young and highly magnetized neutron stars which display a wide
array of X-ray activity including short bursts, large outbursts, giant flares
and quasi-periodic oscillations, often coupled with interesting timing behavior
including enhanced spin-down, glitches and anti-glitches. The bulk of this
activity is explained by the evolution and decay of an ultrastrong magnetic
field, stressing and breaking the neutron star crust, which in turn drives
twists of the external magnetosphere and powerful magnetospheric currents. The
population of detected magnetars has grown to about 30 objects and shows
unambiguous phenomenological connection with very highly magnetized radio
pulsars. Recent progress in magnetar theory includes explanation of the hard
X-ray component in the magnetar spectrum and development of surface heating
models, explaining the sources' remarkable radiative output.
