Read John 16.
Jesus referred to the Holy Spirit as the Helper, or Comforter. "If I do not go away, the Helper will not come to you." (v.7b) The Lord said this to the disciples in the context of preparing them for His leaving and for what His followers would be facing in rejection and tribulation in His absence. The Holy Spirit ministers in several ways mentioned in this chapter.
1. He is the Comforter of believers. (v.7)
Jesus would not leave His followers alone. When Jesus ascended back to heaven in Acts 1, this third Person of the trinity came in Acts 2. As we saw in John 14, the Holy Spirit helps believers by interceding for us in prayer, empowering us for serving Christ, and encouraging us through the difficulties of life.
2. He is a Convictor of sin. (v.9)
A key role of the Holy Spirit is to prick the human conscience when one violates the word of God.
3. He is the Convictor of right. (v.10)
When one sincerely desires to please God and accomplish what He wants done, the Holy Spirit will provide such assurance. With such, by faith, we move forward in decision making. "Now faith is the assurance of things hoped for, the conviction of things not seen." (Hebrews 11:1)
4. He is the Convictor of accountability. (v.11)
Judgment is coming. One day the followers of Jesus will stand before the Judgment Seat of Christ (2 Corinthians 5:10). Those who refused to place their faith in Jesus as their Savior will face eternal punishment at the Great White Throne (Revelation 20:11-15).
5. He is the Guide of all truth. (v.13)
This is primarily a promise to the Apostles that they would be able to write and speak accurately on behalf of God. The New Testament writers take no personal credit but attribute the work to the Holy Spirit. (2 Timothy 3:16; 2 Peter 1:20-21) Guiding believers into the reassurance of God's truth is part of His work above in #3.
6. He is the Glorifier of Jesus. (v.14)
If the Holy Spirit is at work, He will not draw attention to Himself. His role in all five of the works above is to direct people to worship and praise Jesus.