Something which has always confused me is the emergence of the Italian language. Why did the inhabitants of Rome stop speaking Latin, and invent a new language?

From http://en.wikipedia.org/wiki/Italian_language#History

"The history of the Italian language is long, but the modern standard of the language was largely shaped by relatively recent events. The earliest surviving texts which can definitely be called Italian (as opposed to its predecessor Vulgar Latin) are legal formulae from the region of Benevento dating from 960-963[2]. Italian was first formalized in the first years of the 14th century through the works of Dante Alighieri, who mixed southern Italian languages, especially Sicilian, with his native Tuscan in his epic poems known collectively as the Commedia, to which Giovanni Boccaccio later affixed the title Divina. Dante's much-loved works were read throughout Italy and his written dialect became the "canonical standard" that others could all understand. Dante is still credited with standardizing the Italian language."

Italian formed from the common peoples' speech of old rome. It was like the slang of rome. Latin was more formal and to the point. Dante's Inferno helped bring this lower dialect into larger use--as it was the first major recognized work ever written in the dialect. Since then it has evolved much, though.

Bellissimo!

When Dante wrote the Divine Comedy.

People never abruptly stop speaking one language, sit down, and invent a totally new one. Languages can be invented, but natural languages such as Italian simply were not invented. Rather, they evolve from another language gradually through a set of sound changes. Changes in grammar, syntax, and semantics are also common. Just like organisms never literally give birth to a child of a totally new species, the children of the speakers of one language never grow up magically speaking a totally new language. It's all on a spectrum of changes.

This is the story of the emergence of the Italian language, and indeed all other languages, in terms as basic as one can possibly put them. Italian is not at all unique in this process. There are many, many languages just like Latin that gave rise to modern languages such as English, German, Mandarin, Cantonese, etc. Latin was merely one of the best known and most influential ones.