The dude on the right, Charles Messier, lived in France from 1730 to 1817. He was an avid comet hunter and perhaps a distant ancestor of a once famous Edmonton Oiler. He's famous now, not for the comets that he discovered, but for the astronomical objects he catalogued that were not comets. He kept track of them so as not to confuse them with potential comets that might be discovered in the sky.
The list of Messier Objects is the usual starting place of observable objects in the night sky for amateur astronomers. Not all of them require a telescope. For example the Pleiades (also known as the Seven Sisters) star cluster, visible in the winter months, is a Messier Object that can be readily seen with the naked eye. Its number is M45 (Messier 45). Many Messier objects can be seen very well with binoculars. There are 110 objects in the Messier catalogue.
There is only one time of the year when all of the Messier objects can be observed in one evening. This is around the spring equinox (March 20, 21). It should be made clear that this is more than just an "evening"; viewing them all requires starting at sunset and going until sunrise. How come? Because the earth is turning, it's necessary to view the objects after they rise and before they set. The rite of viewing all the Messier objects in one go is known as the Messier Marathon.