Be strong and of good courage, for to this people you shall divide as an inheritance the land which I swore to their fathers to give them. 7 Only be strong and very courageous, that you may observe to do according to all the law which Moses My servant commanded you; do not turn from it to the right hand or to the left, that you may prosper wherever you go. 8 This Book of the Law shall not depart from your mouth, but you shall meditate in it day and night, that you may observe to do according to all that is written in it. For then you will make your way prosperous, and then you will have good success. 9 Have I not commanded you? Be strong and of good courage; do not be afraid, nor be dismayed, for the LORD your God is with you wherever you go.”
According to Wikipedia, "Courage, also known as bravery, will, intrepidity, and fortitude, is the ability to confront fear, pain, risk/danger, uncertainty, or intimidation. "Physical courage" is courage in the face of physical pain, hardship, or threat of death, while "moral courage" is the ability to act rightly in the face of popular opposition, shame, scandal, or discouragement.
In the story of Joshua, God made huge promises to Joshua that he would lead the people into taking the land of promise and that he would be with him as he'd been with Moses. Then God has to tell Joshua to be courageous. He must have needed that because that because of the danger of the task.
From pop-culture, consider that line in the Gilligan's Island song, "if it wasn't for the courage of the fearless crew, the Minow would be lost". In other words, the crew rose to the occasion and did their best at sailing in the storm and saved the lives of all on board. If they were not courageous and froze in fear, the result may have been different.
To encourage to to call up courage in another. The ministry of giving a prophetic word is an encouragement. Whatever form a prophetic word comes in, the result will be encouragement (1 Corinthians 14:3, 31).
At one of king David's low points, it says, "David encouraged himself in the Lord" (1 Samuel 30:6). We have to learn how to go to the well and remember God's love, God's faithfulness, and God's promises and call on our lives.