biblical offspring of the "sons of God" and the "daughters of men"
The Nephilim (Hebrew: נְפִילִים, nefilim) were the offspring of the "sons of God" and the "daughters of men" before the Deluge, according to Genesis 6:1–4.
A similar or identical biblical Hebrew term, read as "Nephilim" by some scholars, or as the word "fallen" by others, appears in Ezekiel 32:27.
When people began to multiply on the face of the ground, and daughters were born to them, the sons of God saw that they were fair; and they took wives for themselves of all that they chose. Then the Lord said, "My spirit shall not abide in mortals forever, for they are flesh; their days shall be one hundred twenty years." The Nephilim were on the earth in those days—and also afterward—when the sons of God went in to the daughters of humans, who bore children to them. These were the heroes that were of old, warriors of renown.
The word is loosely translated as giants in some Bibles and left untranslated in others. The "sons of God" have been interpreted as fallen angels in some traditional Jewish explanations.
According to Numbers 13:33, they later inhabited Canaan at the time of the Israelite conquest of Canaan.
The Lord said to Moses, "Send men to spy out the land of Canaan, which I am giving to the Israelites" ... So they went up and spied out the land ... And they told him: "... Yet the people who live in the land are strong, and the towns are fortified and very large; and besides, we saw the descendants of Anak there." ... So they brought to the Israelites an unfavorable report of the land that they had spied out, saying, "The land that we have gone through as spies is a land that devours its inhabitants; and all the people that we saw in it are of great size. There we saw the Nephilim (the Anakites come from the Nephilim); and to ourselves we seemed like grasshoppers, and so we seemed to them."
Read more or edit on Wikipedia