The word Emmanuel translates to "God is with us." Matthew recalls the messianic prophecy from Isaiah 7:14 and states that its ultimate fulfillment is found in Mary’s Son: "Behold, a virgin shall conceive and bear a son, and his name shall be called Emmanuel" (Matt. 1:23).
"Name," in this sense, does not refer to the actual name Joseph and Mary were to give to their Son (cf. Matt. 1:21, Luke 1:31); in this case, the word is used in the sense of "to call" (i.e., "they shall call his name Emmanuel," cf. Is. 7:14). Analogously, one could say of baseball legend, Babe Ruth, "They called him the Sultan of Swat," without intending to mean that "the Sultan of Swat" was George Herman Ruth Jr.’s given name. Just as Babe Ruth’s nickname was meant to indicate that Ruth was a great hitter, so Emmanuel indicates that the expected Messiah would be "God with us."
Emmanuel, "God is with us," also calls to mind the last verse in Matthew (28:20): "Behold, I [Jesus] am with you always, until the end of the age."