The Holy Spirit is the third person in the Trinity. He is fully God. He is eternal, omniscient, and omnipresent, has a will, and can speak. He is alive. He is a person. He is not particularly visible in the Bible because His ministry is to bear witness of Jesus (John 5:26).
Some cults like the Jehovah's Witnesses say that the Holy Spirit is nothing more than a force. This is false. If the Holy Spirit were merely a force, then He could not speak (Acts 13:2); He could not be grieved (Eph. 4:30); and He would not have a will (1 Cor. 12:11).
The truth is that the Holy Spirit is a person the same as the Father and the Son are within the Trinity.
The Works of the Holy Spirit
 Reasoning from the Scriptures, 1985, pp. 406-407