Charles Messier was a French astronomer who lived between the years of 1730 and 1817. Originally he was one of the first comethunters and recorded nearly all comets that could be seen during his career. When chasing the comets he often was confused by nebular objects that obviously wheren´t comets and didn´t move relatively to the stars.
In order not to confuse them with comets all the time, between 1758 and 1781 he organized a catalogue of 103 of these "nebular" objects. The current Messier catalogue includes 110 objects since 7 more objects that Messier saw have been included since 1924.
The "nebular" objects that Messier assembled in a catalogue are mainly known today as a collection of deep sky objects far away from our planetary system: open clusters, Globular clusters, emission or reflection nebulae and planetary nebulae of our milkyway system as well as galaxies of the local group and external galaxies. Here you can see all 110 Messier objects on one sight: