Short answers, pulled from the story.
Mansa Musa was the ninth Mansa of the Mali Empire, which reached its territorial peak during his reign. He ruled from roughly 1312 to roughly 1337 and is often regarded as presiding over the zenith of Mali's power and prestige.
Mansa Musa made his hajj to Mecca between 1324 and 1325, a journey of about 2,700 miles. He left his son Muhammad to rule Mali in his absence and reached the outskirts of Cairo in July 1324.
Mansa Musa's wealth came principally from the Mali Empire's control and taxing of the salt trade from northern regions and especially from gold panned and mined in Bambuk and Bure to the south. It is estimated that two thirds of the gold circulating in the Medieval Mediterranean came from West Africa.
Under Mansa Musa the Mali Empire covered land now part of Guinea, Senegal, Mauritania, the Gambia, and the modern state of Mali, an area of 1,300,000 square kilometers. At his accession it absorbed the former Ghana Empire, which had become a vassal of Mali.
According to al-Umari, before Mansa Musa's arrival a mithqal of gold was worth 25 silver dirhams, but it dropped to less than 22 dirhams afterward and stayed there for at least twelve years. The historian Warren Schultz has argued this was within the normal fluctuations of gold value in Mamluk Egypt.
Historians such as Hadrien Collet argue that Mansa Musa's wealth is impossible to calculate accurately. Encyclopedia Britannica calls him widely considered the wealthiest person in history, but the Catalan Atlas of 1375 described him only as the richest man in the region.