As sky123 already said, "Immanuel" means "God with us" in Hebrew.
"Immanuel" sometimes is seen as another name or title for Messiah or Christ.
There is the following line in the Old Testament, when Isaiah is talking about the coming Messiah:
Isaiah 7:14: "Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel."
In the New Testament, Mathew quotes that, referring to Jesus.
Matthew 1:23: "The virgin will conceive and give birth to a son, and they will call him Immanuel”[a] (which means “God with us”)."
There is an old Advent song, "Veni veni Emanuel (Emanuel is the Greek version of Immanuel), which is Latin for: "Come, come, Immanuel."
From what I have learned, Immanuel usually refers to Messiah/Christ and his arrival.
The King's Singers are performing that old song beautifully:
https://www.youtube.com/watch?v=wE6BzoMt0Ro