Eta Carinae is one of the most massive stars known in the Galaxy, a binary system with a period of 5.54 years showing regular so-called 'spectroscopic events', under which the spectrum changes drasticaly in many wavelength regions. The star is in an unstable phase with major mass loss events of which 'the Great Eruption' ejected in 1840s has a mass of 10 solar masses, and now appears as the well known bipolar nebula. The expelled mass also forms a disk-like structure. Ejecta from less massive eruptions prior to and after this event can also be observed, and show similar structures.
I will review the present understanding of the star, including an unexpected recovery from the previous event in January 2009. Focus will be put on the spectroscopic investigations of the Strontium Filament and the Weigelt condensation and their peculiar abundances. These regions also work as laboratories for atomic photo-processes under extreme conditions.
