Sanctified Reason - What Exactly is the Baptism of the Holy Spirit?

Spirit-filled Christians do not all view "the baptism of the Holy Spirit” in the same way. Some teach that believers need to experience a “second blessing” in order to be baptized with the Holy Spirit, while others teach that every believer is baptized with the Holy Spirit at the moment of conversion. (1 Corinthians 12:13) So who is correct?