"'About noon as I came near Damascus, suddenly a bright light from heaven flashed around me. I fell to the ground and heard a voice say to me, "Saul! Saul! Why do you persecute me?" "Who are you, Lord?" I asked. " I am Jesus of Nazareth, whom you are persecuting," he replied.'" NIV translation
Saul had a little talk with Jesus on the road to Damascus. Jesus made a dramatic entrance and got Saul/Paul's attention. Jesus immediately asked him about his sin in order to bring Paul to understand his need for repentance. This is the same dramatic type of thing that occurs in everyone who comes to Christ. If you can't remember Jesus showing up in your life, you might want to check yourself to make sure that you have actually met Him.
"'My companions saw the light, but they did not understand the voice of him who was speaking to me.'" NIV translation
Paul continues to describe his encounter with Jesus and there were witnesses who saw the light. They heard Jesus speaking to Paul but could not understand what He was saying. Jesus was giving a specific message to Saul/Paul and his companions did not need to understand or God would have allowed them to do so. There are those that say that God/Jesus does not audibly speak to people today but there is no basis for putting such a limit on God. If He wants to tell you something, He can! (What He tells you will line up with his Word and purpose.)
"'What shall I do, Lord?' I asked. 'Get up,' the Lord said, 'and go into Damascus. There you will be told all that you have been assigned to do.'" NIV translation
When Paul came face to face with the Lord, his reaction was to fall down in worship and then it was to find out how he was to serve. Jesus told Paul that he had been assigned things to do and we may say he's Paul and God had great things planned for him which is true. But, God has also planned great things for each of us to do as Paul tells us in Ephesians 2:10.
"My companions led me by the hand into Damascus, because the brilliance of the light had blinded me." NIV translation
We might ask ourselves why God would blind Paul just as he was having a change of heart. As we shall see, God is working behind the scenes for the good of His servant. We will have some tough things happen in our walk with Christ walking through these valleys is a normal part of our growth. (see Nehemiah 3 for a look at the valley gate and its role in our walk.)