What is faith?

What is faith? We talk so often about having faith, but what is it? How does it help us when we are struggling, discouraged? Is it like an ostrich sticking its head in the sand, a refusal to acknowledge your surroundings or a conflict? Is it an attempt to side-step hard things because “I have faith God will fix this”? What is the writer of Hebrews trying to help us understand about the nature of faith? What does it really do? How does it help us hold fast to who God is and what he has spoken to us through his word?