Okay, so God's Son is super important—that's why his followers need to pay really close attention to what they've been taught about him. Otherwise, they might start getting a little lazy about this whole following God thing. No one wants that.
After all, says Hebrews, God gave the world the Torah (a.k.a. the first five books of the Hebrew Bible) to tell us to expect his son. And the Jewish prophets backed him up. Then God showed off by letting all kinds of miracles happen to show the truth. Finally, he went and gave the world the Holy Spirit. Message received, God.
Quick side note: folks who believe that Jesus is the son of God tend to interpret the Hebrew Bible/Old Testament as a precursor of the New Testament—they believe that parts of the Hebrew Bible predict the birth (and story) of Jesus and that the New Testament is basically a fulfillment of the Old. But folks who just use the Hebrew Bible (namely, Jews) would argue that Christians are projecting this reading onto the scripture where it doesn't exist. For our part, we don't really care who thinks what—we're reading this as literature, and we're going to analyze it as such.
Back to Hebrews: when the world needed a savior, did God send an angel? Nope. (Yeah, this point is really being hammered home). He sent his son. Oh, did we mention? His name is Jesus.
Even though Jesus is totally equal with God, there was a time when he "was made lower than the angels" and became a human being.
After he suffered and died (see the Gospels for the full story there), Jesus got all kinds of glory and honor from God. Way to make the Old Man proud.
He also performed a pretty neat little trick. When he died, Jesus "tasted death for everyone." Sounds…delicious?
Basically, that just means that, by suffering and dying, Jesus became "perfect," and was able to show the rest of the world how to perfectly follow God as well. All in a days work for the savior of the world, we guess.
But why do it? Well, Jesus and the rest of the world have one dad: God. That means every single human being is like Jesus's brother or sister.
Jesus needed to save God's children, so he became just like them—i.e., flesh and blood. He died, just like regular people, so that he could dropkick the devil (figuratively, of course) and make it so that no one ever had to be afraid of dying again.
Remember, Jesus didn't come to help the angels—he came to help people. That's why he became a human being and not an angel. Sorry, angels.
Jesus became like a Jewish high priest who made a sacrifice for all the people. In this case, the sacrifice wasn't a ram or a goat—it was himself.
Since Jesus lived and suffered and died just like humans do, says Hebrews, he totally feels people's pain when they've got a problem.