Who is Emmanuel??

I’m reading Dauoy Rheim’s translation and in Isaias 7:14 it says, “Therefor the Lord himself shall give you a sign. Behold a Virgin shall conceive, and bear a son, and his name shall be called Emmanuel.”

Who is Emmanuel? Is he Jesus? Why is he Emmanuel instead of Jesus? In Luke 1:31 “Behold thou shalt conceive in thy womb, and shalt bring forth a son; and thou shalt call his name Jesus.”

Is this a different language sort of deal?