The Nicolaitans were the followers of a heresy that had infiltrated the early church. In the book of Revelation, Jesus condemned the practices of the Nicolaitans and warned his people not to follow their mistakes.
The Bible does not explain who the Nicolaitans were, nor does it tell us what they believed. It just says that their practices were hateful to God. The problem was so serious that a church where its teaching had infiltrated was in danger of being destroyed! – Revelation 2: 15-16
The name of most religious parties, sects and heresies came from their founder or someone who served as an inspiration for the group. Therefore, the Nicolaitans probably took their name from someone named Nicholas .
Some traditions claim that the founder of the heresy was Nicholas, one of the seven men chosen by the church to serve, along with Stephen ( Acts 6: 3-5 ). However, other older traditions deny this association. Considering the excellent reputation of Nicholas and his companions in the Bible, it is unlikely that he was the founder of this hateful sect. The Nicolaitans may have used his name to give the group more credibility or they may have been founded by another Nicolau.
See here: what is a sect?
What were the detestable practices of the Nicolaitans?
The Bible does not say what the sins of the Nicolaitans were, but their influence in the church was a serious danger. They were present in at least two cities: Ephesus and Pergamos. The church in Ephesus struggled against its teaching ( Revelation 2: 6 ) but the church in Pergamos did not. Because of that, this church was in trouble.
The Pergamon church had a problem with idolatry . Revelation 2: 14-15 shows that believers were falling into the same mistakes as the people of Israel in the desert, many centuries before. A man named Balaam had induced the people of Israel to commit idolatry and sexual immorality . Now some Christians were participating in idolatrous parties and promoting immorality! In addition, they still tolerated the Nicolaitans.
Find out here: who was Balaam?
Nicolaitan practices may have some connection with the sins of Balaam’s followers, of idolatry and immorality. Their teachings may have reinforced the practices of this other group. Or, the sins of the Nicolaitans may have been different, but the spiritual confusion in the church at Pergamos was worsening.