Isaiah 7 contains one of the best known texts in that book, used by Matthew to point to the coming of Jesus: “The virgin will be with child and will give birth to a son, and will call him Immanuel” (vs. 14).
But you should keep two things in mind: First, the word “virgin” can also be translated “young woman” and second, the message Isaiah is giving originally had nothing to do with Jesus.
The situation is that the Northern Kingdom of Israel has allied herself with Syria (called Aram). Together, these two nations have marched on the Southern Kingdom of Judah. Judah and her king, Ahaz, is petrified. But God speaks to them through Isaiah and tells Ahaz: “Keep calm.” The opposing army will not succeed. Before a young woman can conceive and bear a son and that son grow to know the difference between right and wrong, the enemies he faces now will cease to exist.
But instead, there will come another enemy: Assyria.
Why? To punish God’s people (Judah) for their sins.
You will see a similar sign pointing to the same thing in chapter 8.
Old Testament prophecies sometimes have two meanings: the one intended when the prophecy occurred, and a more distant one revealed by the New Testament. You know the first one by context, but the only way you know the second one is when it is actually revealed in the New Testament.