  We present a brief overview of the main effects by which a star will have an
impact (positive or negative) on the surface habitability of planets in orbit
around it. Specifically, we review how spectral, spatial and temporal
variations in the incident flux on a planet can alter the atmosphere and
climate of a planet and thus its surface habitability. For illustrative
purposes, we emphasize the differences between planets orbiting solar-type
stars and late M-stars. The latter are of particular interest as they
constitute the first sample of potentially habitable exoplanets accessible for
surface and atmospheric characterization in the coming years.
