The gamma-ray burst of the ninth of October of 2022 (GRB 221009A) was the brightest ever recorded. It saturated most of the gamma-ray detectors in space and even affected the Earths ionosphere. On ground, Cherenkov detectors measured photons of up to 18 TeV, never seen before for these objects. It's brightness allowed amateur telescopes to observe it for days, and by major facilities for months. It was a very luminous GRB, but what made it truly extraordinary, and a likely once-in-a-lifetime event was the combination of this luminosity with its low redshift. Unfortunately, GRB221009A was hidden behind a large amount of galactic dust, which complicated the analysis and interpretation of the observations. Here we present a detailed compilation of observations of this event, many previously unpublished. This includes extensive spectroscopic data from 8-10m ground-based telescopes, from space with HST and JWST, and multi-wavelength photometric observations from radio to X-rays. I will review the knowledge on this event and give a further insight to the physics of the event, its associated supernova, and host galaxy environment. Finally, I will place its significance in the context of extreme astronomical transients and will detail the lessons that this extraordinary event has taught us.