The Holy Spirit
The Bible reveals Yahweh, the God of the universe, as the one and only God and that no other God has existed or will ever exist. The Bible also reveals that Yahweh is one in His essence or substance and, as one essence, exists as three persons called the Father, the Son, and the Holy Spirit. The placement of the Holy Spirit in progressive revelation as well as the role of the Holy Spirit in revealing the things of the Father and Son (John 16:15) make Him the least conspicuous person of the Trinity. The Holy Spirit functions by thrusting the Father and Son into the spotlight and keeping Himself primarily out of the limelight.
Two version of notes are available: notes for the Getting to Know the Holy Spirit class and Dave’s extended notes, which add greater detail to a study on the Holy Spirit.