A witness shares what they have personally experienced. In Acts 1:8 Jesus calls believers to be His witnesses, and in Mark 5 we see this when the demon-possessed man is completely restored—calm, clothed, and in his right mind—showing the wholeness (sozo) Jesus brings. Instead of making him a preacher, Jesus sends him to simply tell others what the Lord has done. Our testimony glorifies God, encourages others, and points people to Jesus.