Short answers, pulled from the story.
The Battle of Naissus was a battle fought in 268 or 269 in which Roman forces defeated a large coalition of Gothic and allied tribes near Naissus, in modern Niš. The victory was part of Rome's response to major invasions during the Crisis of the Third Century.
Ancient sources disagree on which emperor commanded at Naissus, crediting either Gallienus or his successor, Claudius II Gothicus. Modern scholarship generally credits the final victory to Claudius II, while the future emperor Aurelian, who led all of Claudius' cavalry, appears to have led the decisive charge.
Some 50,000 Goths were allegedly killed or captured after Roman forces lured them into an ambush with a feigned retreat. This figure comes from ancient sources and is treated by modern historians as an extraordinary, possibly exaggerated, toll.
Survivors fled toward Macedonia and formed a defensive laager, but hunger, Roman cavalry harassment, and an epidemic at Mount Haemus wore them down. Rome eventually absorbed the prisoners into its army or settled them on land as coloni.
The battle largely removed the threat from Germanic tribes on the Balkan frontier for decades afterward. It also gave Claudius the title Claudius II Gothicus Maximus, meaning conqueror of the Goths, though he died from an epidemic linked to the campaign in 270.
Ancient sources such as the Augustan History and Zosimus claim the second, larger invasion involved between 2,000 and 6,000 ships and 325,000 men, though this is probably an exaggeration. The coalition included Goths of the Greuthungi and Thervingi peoples along with Gepids and Peucini, led by the Heruli.