The Gauls (Paraphrased from Wikipedia because I'm lazy!).
Religion
The Gauls practiced a form of animism, ascribing human characteristics to lakes, streams, mountains, and other natural features and granting them a quasi-divine status. Also, worship of animals was not uncommon; the animal most sacred to the Gauls was the boar, which can be found on many Gallic military standards, much like the Roman eagle.
Depiction of Cernunnos from the Pilier des Nautes, Paris, France.Their system of gods and goddesses was loose, there being certain deities which virtually every Gallic person[citation needed] worshiped, as well as tribal and household gods. Many of the major gods were related to Greek gods; the primary god worshiped at the time of the arrival of Caesar was Teutates, the Gallic equivalent of Mercury. The "father god" in Gallic worship was "Dis Pater," who could be assigned the Roman name "Jupiter." However there was no real theology[citation needed], just a set of related and evolving traditions of worship.
Perhaps the most intriguing facet of Gallic religion is the practice of the Druids. There is no certainty concerning their origin, but it is clear that they vehemently guarded the secrets of their order and held sway over the people of Gaul. Indeed they claimed the right to determine questions of war and peace, and thereby held an "international" status. In addition, the Druids monitored the religion of ordinary Gauls and were in charge of educating the aristocracy. They also practiced a form of excommunication from the assembly of worshippers, which in ancient Gaul meant a separation from secular society as well. Thus the Druids were an important part of Gallic society.
Government
Gaulish society was dominated by the druid priestly class. The druids were not the only political force, however, and the early political system was complex. The fundamental unit of Gallic politics was the tribe, which itself consisted of one or more of what Caesar called "pagi". Each tribe had a council of elders, and initially a king. Later, the executive was an annually-elected magistrate. Among the Aedui tribe the executive held the title of "Vergobret", a position much like a king, but its powers were held in check by rules laid down by the council.
The tribal groups, or pagi as the Romans called them (singular: pagus; the French word pays, "region", comes from this term) were organised into larger super-tribal groups that the Romans called civitates. These administrative groupings would be taken over by the Romans in their system of local control, and these civitates would also be the basis of France's eventual division into ecclesiastical bishoprics and dioceses, which would remain in place with slight changes until the French Revolution.
Roman silver Denarius with the head of captive Gaul 48 BC, following the campaigns of Caesar.Although the tribes were moderately stable political entities, Gaul as a whole tended to be politically divided, there being virtually no unity among the various tribes. Only during particularly trying times, such as the invasion of Caesar, could the Gauls unite under a single leader like Vercingetorix. Even then, however, the faction lines were clear.
The Romans divided Gaul broadly into Provincia (the conquered area around the Mediterranean), and the northern Gallia Comata ("free Gaul" or "wooded Gaul"). Caesar divided the people of Gaulia Comata into three broad groups: the Aquitani; Galli (who in their own language were called Celtae); and Belgae. In the modern sense, Gaulish tribes are defined linguistically, as speakers of dialects of the Gaulish language. While the Aquitani were probably Vascons, the Belgae would thus probably be counted among the Gaulish tribes, perhaps with Germanic elements.
Languages
Gaulish or Gallic is the name given to the Celtic language that was spoken in Gaul before the Vulgar Latin of the late Roman Empire became dominant in Roman Gaul. According to Julius Caesar in his Gallic Wars it was one of three languages in Gaul, the others being Aquitanian and Germanic. In Gallia Transalpina, a Roman province by the time of Caesar, Latin was the language spoken since at least the previous century. Gaulish is paraphyletically grouped with Celtiberian, Lepontic, and Galatian as Continental Celtic. The Lepontic language and the Galatian language are sometimes considered to be dialects of Gaulish. Gaulish is a P-Celtic language and (like Lepontic in Cisalpine Gaul) was already spoken in Gaul long before the arrival of the Gallic tribes in the 6th century B.C.