Vlachs were the romanized Dacian/Thracian (some theories say that even Illyrian or Greek) people from the Balkans. Their place of origin is hard to be determined as they can be found all over the Balkan peninsula, including Greece, Bulgaria, Albania and the Republic of Macedonia.
Their occupations were mostly trading, shepherding and craftmanship.
The first record of possible Vlach settlement is found in the writings of Procopius, in the 5th century: the forts named Skeptekasas (Seven Houses), Burgulatu (Broad City), Lupofantana (Wolf's Well) and Gemellomuntes.
In 586, the first written record of their name and their language appears on a Byzantine chronicle about an incursion against the Avars in Eastern Balkans. When the baggage of a mule slips, the muleteer shouts "Torna, torna, frater" (Return, return, brother!), although it might just be the last appearance of Latin.
In the 7th century, in the Acts of Saint Demetrius, it is related how the Avar Khan deported from Illyricum to Smirnium, in Pannonia 270,000 people "that followed the Roman tradition" and they might be the ancestors of Romanians.
In the 10th century, the Hungarians arrive in the Pannonian plain and according to the anonymous chancellor of King Bella III of Hungary the plain was inhabited by Slavs, Bulgars, Vlachs and "pastores Romanorum" (Roman shepherds), although this late writing (1146) might be slightly inaccurate.
Today, the official position of the Greek government is that the Vlachs are only Greeks speaking a latin dialect (so they are not admited to be a national minority -- in fact, Greece does not recognise any minorities), although there is not enough evidence in favour of this claim, and as a consequence they are not encouraged to keep their language and traditions, but encouraged to "return" in speaking "the language of their ancestors".