This has most certainly been asked before, but I couldn't seem to find anything. I know they were separated by 1000 years, but were they the ancestors to the Mongols, an entirely different culture, or do we even know for sure since they were bad at keeping written records?
The Huns were a different culture to the Mongols.
The origins of the Huns are still debated today, in the 18th century the French scholar de Guignes proposed that the Huns were related to the Xiongnu, a nomadic people who emigrated out of northern China in the 1st century CE. However, the evidence for this theory is not definitive, and so it is not universally accepted.
Due to poor archaeological records, and an absence of a written language, it is very difficult to establish where the Huns came from. Nowadays people tend to lean more towards the idea that they came from the steppes of Central Asia, though the precise location is unknown.
They first appear in written records by Tacitus, who says that they live near the Caspian Sea in 91CE. But they don't make their way into Europe until the 4th century.
On the other hand, we have the Mongols, whose empire began in 1206CE, with the Mongol clans united under Genghis Khan. Their homeland was Mongolia, but upon Ghengis' death in 1227, the empire stretched from the Pacific to the Caspian sea.
Their forays into Europe began in 1237CE, when Ghengis' grandson Batu led an attack on Kievan Rus (a federation of tribes centred in Eastern Europe). They would continue to push westward, through modern day Ukraine, Poland and Germany until they reached Albania and Austria. However, in 1241CE, Ghengis' successor Ögedei died, and as was customary, the princes of Ghengis' line had to return to Mongolia to elect his successor.
It must also be mentioned, that whilst the Huns kept no written records, the Mongols did. We are very fortunate that a work from c.1227CE called The Secret History of the Mongols survives to this day. It is made up of 12 chapters and deals with the life of Ghengis, as well as elements of Mongolian folklore and practices. It survived due to it being translated into Chinese (Ghengis' grandson Kublai Khan established a dynasty in China called the Yuan dynasty). Whilst not the most reliable source in terms of historical accuracy, it is nevertheless incredibly important as a primary source for Ghengis' life, and for Mongolian poetry.
To be very general since I don't know much about the Huns, they were a group of nomadic people much like the Mongols in many ways. They lived in western Asia and had brief success conquering much of Europe.
The Mongols, as you said, came at a later time and conquered much of Asia. The Huns are sometimes cited as an earlier example of the success that the Mongols would have had in Europe if it hadn't been for their king's death and the subsequent division of the Mongol empire.
The Mongols and the Huns under Attila both share the common infamy in history of being extremely barbaric and ruthless towards their enemies. The difference is, the Mongols' impact on history was much more significant due to their larger success.