M42 (aka NGC 1976) and M43 (aka NGC 1982), which is smaller and to the right (North) of M42, form the Orion Nebula located about 1,344 light-years away in the much larger Orion molecular cloud of the Milky Way.  The Orion Nebula is the brightest nebula in our sky and is visible by the naked eye as the middle, albeit fuzzy, "star" in Orion's "sword".  M42 and M43 are separated by a dark band of dust called the northeast dust lane (aka "the Fish's Mouth").   Extensively studied, M42 is about 24 light-years across, has a mass of about 2,000 suns, and is a region of major star formation.  

Just to the left (South) of the Fish's Mouth is a tight, bright, open cluster of young stars called the Trapezium (aka Theta1 Orionis), so named for the four brightest O-type stars closely located only 1.5 light-years of each other.  O-type stars are the hottest, most massive, and represent only 0.00003% of all stars.  

Located at the left corner of the Trapezium in this picture is the brightest of these O-type Trapezium stars, Theta1 Orionis C1, which is 33 times the mass, 204,000 times the luminosity, and almost 7 times hotter than our Sun.  It's stellar wind is also a hundred thousand times stronger than the Sun's.  Theta1 Orionis C is actually a binary star system with an 11 solar mass companion, C2, orbiting around C1 every 11 years.  The fifth brightest of the Trapezium stars is about 15 solar masses and is resolved in the glare of the other four in this picture.  In total, there are 17 stars within the 1.5 light-years diameter of the Trapezium cluster, as well as a possible intermediate mass black hole having 100 solar masses.  

At the far left (South) of this picture is the 2.8 magnitude naked eye star Iota Orionis, which is seen in the sky as the southern tip of Orion's sword.  The bluish nebulosity between Iota Orionis and the red of M42 is NGC 1980.

-Wikipedia

The stars in this picture have been processed separately and diminished to better show details in the nebula.  The Orion Nebula is hard to process because of the great brightness difference spanning between the Trapezium and the darker dust lanes.  The stars were extracted from the nebula in both the 10 and 200 second masters using Star-X-Terminator to enable separate processing.  Only the 200 second "nebula-only" master was subsequently used.  In this image, the brightness of the nebula around the Trapezium was reduced to better show nebular structures as well as resolve 5 of the Trapezium stars.  Both 10 and 200 second "star-only" masters were combined using the HDR Composition tool to reduce the halos around the bright saturated stars enabling better resolution of the Trapezium and other bright stars.  The processed 200 second "nebula-only" master was then recombined with the processed 10/200 HDR  "star-only" master to generate the final picture.