This is the NGC 6559 Nebula Complex, a star-forming region that is located within the Sagittarius constellation (some 5,000 light-years from Earth).
The region is split up into several different nebulae types. Firstly, NGC 6559 can be seen in the bright red and blue portions of the image. The red area is home to a large concentration of hydrogen gas (with a smattering of heavier elements), which will collapse to give life to new stars. Whereas, the blue area located nearby is already home to many energetic new stars. When their starlight comes in contact with interstellar grains of dust within the clouds, it scatters - thus creating a reflection nebula.
Speaking of scattering --- we also have B 303 (a dark nebula). It's the wispy black cloud that drapes over the scene. This region is also composed of a rather large collection of interstellar dust grains. Yet in this case - thanks to the density of the dust, the stars embedded within the cloud are obscured from view at optical wavelengths.
Lastly; whilst the region looks quite large, in actuality, it's merely a few light-years across. Still, 3 light-years is a stunningly vast expanse of space. One so large, it's almost incomprehensible on a human-scale. For example, light could make a round-trip through our solar system before it could travel from one side of this region to the other one. (The universe is pretty cool!)