Rugby football history began in 1823 when William Webb Ellis, a student of the Rugby School (Rugby, England), while playing soccer first took the ball in his arms and ran with it and that became a distinctive feature of the new-invented game.
Also it is said that Webb Ellis' father was stationed with English troops in Ireland where he saw the Irish native game called Caid (Cad) and showed it to his son. All branches of the Celtic race played Caid. That's why many of rugby fans state that rugby football is the most ancient football game taking its origin from ancient Celts or even Romans or Greeks. And rugby football history is extremely ancient as well.
But it's all an urban legend. The actual rugby football history says that between 1750 and 1823 at Rugby School a specific football game where the handling of the ball was allowed had been developed. But at that time running with the ball was forbidden and only by 1841-1842 it had been legalized. There were no fixed limits for the number of players in each competing team and it might be hundreds of people taking part in the game.
By 1860 a number of schools besides Rugby had been playing football according to Rugby rules. Many rugby clubs appeared but they couldn't come to an agreement as for the game rules. The most debatable matters were those of "Hacking" and "Tripping". Many of rugby clubs (e. g. that of Cambridge University) claimed to ban those game elements. Whereas Rugby School club was against their abolishing the game.
The debates lasted till 1871 when the Rugby Football Union was founded. The rules of the Rugby Football Union made "Hacking" and "Tripping" illegal. The establishment of the Rugby Football Union was an important event in rugby football history, because it initiated the process of rugby rules standardization which resulted in rugby's turning out into separate developed sport.
The history of Rugby Union is the history of gentlemen's rugby. It began in 1871 by the historic meeting of the representatives from 21 clubs in the Pall Mall Restaurant in London. The initiator of the meeting was a certain Edwin Ash the Secretary of Richmond Club, who made a request to all clubs which played rugby for creating a united code of practice because various clubs played to their own rules that made it difficult to play the game among them.
Together with the Rugby Football Union establishing a committee was formed. The main task of the committee was to formulate a set of rules for rugby. As all the committee members were lawyers they formulated not "rules" but "laws". "Laws" for playing rugby. The laws have greatly changed since then but basic ones remain unchangeable even nowadays.
The next important point in rugby football history was 1895 when the history of Rugby League was started. In 1895, the Rugby Football Union split and the so-called Northern Rugby Football Union (NRFU) was formed. That led to the division in rugby football. The rules of NRFU soon changed and the organization, which supported NRFU, changed their rules as well. Then the clubs playing to those new rules changed their names from union to league.
As a result of those events we have now two versions of rugby: the rugby union and the rugby league. The other rugby versions are the derivatives of the above-mentioned rugby union or rugby league.