About the Objects
Bode's Galaxy, the bright spiral galaxy just to the left of center in this image, is a "grand design spiral" meaning it has prominent, well defined spiral arms which extend around the entire galaxy. It is one of the nearest spiral galaxies to our own Milky Way at a distance of roughly 12 million light years. Because of its proximity and relative brightness it is a favorite target for amateurs and professionals alike. The galaxy was first discovered by Johann Elert Bode in 1774 and was first cataloged as "Bode's Nebula" before galaxies were known to be separate island universes rather than nebulous regions within our own galaxy. 

The Cigar Galaxy, on the right side of the image, is a starburst galaxy that is undergoing a wave of new star formation, likely caused by a recent gravitational interaction with Bode's Galaxy (M81) when the two passed near each other. The Cigar (M82) is the nearest starburst galaxy to the Milky Way and is considered the prototype for this class of object. Until 2005 it was thought to be an irregular galaxy, but recent observations of spiral arms have caused it to be re-classified as an edge on spiral. The bipolar outflow ("superwind") streaming from the core of M82 where there are four bright cores of star formation that include strong x-ray sources. Periodic supernovae within the clumps are thought to be the source of the outflow.

You will notice that the background regions around these two galaxies appear to be filled with luminous dust and gas. This material is called the "integrated flux nebula" or "galactic cirrus". It is thought to be interstellar dust and gas located well above or below the plane of the Milky Way that is light up by the integrated light of the entire galaxy rather than by a single star or cluster of stars. This Integrated Flux (IFN) was possibly observed visually as long ago as the 1780's by William Herschel, but Herschel's descriptions were limited to a couple sentences in his notes, and the IFN was quickly forgotten. Though there have been periodic mentions of high galactic latitude nebulosity, the IFN wasn't truly rediscovered until 2005 by California amateur astronomer Steve Mandel using sensitive CCD cameras and a wide field telescope. Imaging the IFN requires very dark skies with minimal light pollution as well as good technique and plenty of integration time.

About the Image
Note that there is an annotated image posted in addition to the luminance master. In addition to M81 (Bode's Galaxy), M82 (The Cigar Galaxy) and the integrated flux, PixInsight and HyperLEDA were able to identify 35 PGC galaxies and an additional 204 faint galaxies from the Sloan Digital Sky Survey, the 2MAS catalog, and a few other more obscure sources. Limiting magnitude appears to be around 23rd magnitude.

One interesting entry I noticed was GHOSTS1, a faint 21st magnitude dwarf galaxy between and below M81 and M82 in this image. GHOSTS1 was discovered by the Hubble Space Telescope in 2012 or so while doing a survey of galactic halos. I believe GHOSTS1 holds the current record for least luminous dwarf galaxy. Despite lying relatively nearby at 39 million light years, it only shines at 21st magnitude.

While GHOSTS1 may be intrinsically very dim, most of the tiny, faint galaxies in the image are just very far away. The most distant galaxies I could find in the image with readily available radial velocity measurements are about 6 billion light years away (1,900 M Parsecs). This assumes a Hubble constant of 70 km/s per mega parsec.