You shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me Acts 1:8

A witness is one who testifies what he has seen or heard or knows. Witnessing about God is testifying what you have experienced firsthand of the reality of God. It is not an effort to explain a church doctrine or a scripture verse, but telling what He has done personally for you. When you tell the truth about what the Lord has done for you, you are not alone. He who believes in the Son of God has the Witness in himself, and He will empower you to be a true witness!