The only information that we have on the Nicolaitan movement is found here in Revelation 2:6 and 2:15. Irenaeus linked this movement with Nicolaus, who was one of the seven deacons in Acts 6:5, but it is doubtful that this was a valid account (Against Heresies 1.26.3). Another church father—Clement of Alexandria—argued that this was false (Stromata 2.20). Osbourne speculates that this could be a Gnostic false teaching, because of the mention of Balaam in verse 14. This is also mentioned in 2 Peter 2:15 and Jude 11, which is linked to a Gnostic, licentious false teaching. He also argues that the language of the “deep things of Satan” could likewise be Gnostic language (Rev. 2:24). While the teachings of the Nicolaitans are unclear, their practices are crystal clear. The text tells us that their primary sin were idolatry (v.14) and sexual immorality (v.20-21; Greek porneia).
 Osborne, Grant. Revelation. Baker Exegetical Commentary on the New Testament. Grand Rapids, MI: Baker Academic. 2002. 120.