Short answers, pulled from the story.
The Huns were a nomadic people who originated in Central Asia and were first recorded living east of the Volga River in a region then considered part of Scythia. By 370 CE they had arrived at the Volga, setting off a chain of migrations across Europe. The 18th-century French scholar Joseph de Guignes first proposed that they were descended from the Xiongnu of northern China, a connection that remains contested.
Attila ruled jointly with his brother Bleda from 434 and became sole ruler after Bleda's death in 445. His major campaigns included invasions of the Balkans in 447, an assault on Gaul in 451 that culminated in the Battle of the Catalaunian Plains, and a 452 invasion of Italy that reached as far as the vicinity of Mantua, where Pope Leo I persuaded him to withdraw. He died in 453.
The Battle of the Catalaunian Plains, fought in 451 in the Roman province of Gaul, pitted Attila's forces against a combined army of Romans and Visigoths commanded by Flavius Aetius. The Huns had previously besieged Orleans before Aetius relieved the city. The battle is generally regarded as a Hunnic defeat or stalemate, and it halted Attila's advance into the Western Roman Empire.
The Hunnic language is almost entirely unknown. Only three words are recorded in ancient sources as being genuinely Hunnic, and all three appear to belong to an Indo-European language. The rest of the evidence comes from personal names and tribal names, from which scholars have proposed Turkic, Mongolic, Eastern Iranian, and Yeniseian affiliations; given how little survives, many consider the language unclassifiable.
The Huns' primary weapon was the composite reflex bow, measuring between 120 and 150 centimeters, made of flexible wood, antler or bone strips, and animal sinew. They attacked in wedge-shaped formations, fired arrows at a distance, then closed to fight with iron swords. They also used plaited cloth nooses to entangle and immobilize opponents. A feigned retreat followed by a sudden reversal was an important tactic noted by multiple ancient writers.
After Attila's death in 453, his son Ellak led the Huns against a Germanic coalition under the Gepid king Ardaric at the Battle of Nedao around 454, where the Huns were defeated. Attila's son Dengizich continued fighting the Romans until he was defeated and killed in Thrace in 469. After Dengizich's death the Huns appear to have been absorbed by other groups, including the Bulgars, though some scholars argue they continued as the Kutrigur and Utigur Hunno-Bulgars under Attila's son Ernak.