But the flourishing epoch of Popular Latin began when Roman colonists faced Celtic, Germanic, Thracian, Illyrian and Iberian lands and peoples. Here mixing with so various nations turned Latin into varieties of dialects, and it's them that are called Popular Latin. It existed on vast territories of Europe since the 2nd century and till the 6th century AD, until it turned into national Romance languages: Old French (Langue d'oil), Old Provencal (langue d'oc), Spanish, Portuguese, Rumanian, Rumantsch etc. Nowadays Romance languages are numerous, with numerous dialectal groups, but the source was only one - Popular Latin.
Great phonetic changes were one of the main features of Popular Latin. New sounds appeared (like [dj], [j], [sh], [ch], sibilants, aspirants, dentals like [th], [ts]), diphthongs almost disemerged, final consonant dropped practically everywhere.
Such phonetic revolution led to grammar changes. Popular Latin carried a tendency to an uninflected language. From the six Latin noun cases, only 3 or 4 (in pronouns) remained here, and afterwards even 2 cases, for other cases were expressed simply by prepositional nouns - the way it is done now in English and French. The definite (from demonstrative pronoun ille) and indefinite (from numeral unus) appeared, as well as the 3rd person personal pronouns which Latin lacked. They also were formed from demonstrative pronouns. The verb system, so terribly complicated in Latin, was altered, and since then auxiliary verbs started expressing perfect, preterite, plusquamperfect and future forms. The only thing that was preserved was the infect verbal endings.
Popular Latin with all its varieties has much in common everywhere among
Romance languages, but the dialectal features depend on the region, on
the nation which used to live here before Romans came and assimilated it.