Nicodemus is a Pharisee, described as a teacher and leader of the people, and a member of the Sanhedrin. While he is mentioned again in John 7:50-52 (defending Jesus in Jerusalem, briefly) and John 19:39-42 (the burial of Jesus), nothing else about him from church history.
His name was probably Naqdimon in Hebrew / Aramaic, and it does not appear to have been common. Richard Bauckham surveyed all occurrences of the name in the Rabbinic literature and Josephus and concluded that all refer to the same family (ben-Gurioin), a wealthy, philanthropic from Jerusalem before A.D. 70. There are several opulent priestly homes excavated around the Temple Mount (the Burnt House, the Caiaphas’ house, etc.) which indicate that a man like Nicodemus could have been well-placed socially in the aristocracy of Jerusalem.
Does Nicodemus become a believer as a result of his encounter with Jesus? An impressive number of scholars describe Nicodemus as a timid follower of Jesus, a secret follow who slowly realizes that Jesus is the true Messiah. But as Andreas Köstenberger points out, John does not use term “believer” to describe Nicodemus, nor is does he give testimony to the true nature of Jesus. Other than his involvement at the burial of Jesus, there is little to suggest he is anything more than a respectful Jewish rabbi similar to Gamaliel in Acts 5. Nicodemus may be interested in Jesus, but never truly believes he is the Messiah.
Is Nicodemus polite and friendly, or is he looking to trap Jesus? His words are similar to the scribes in Matthew 22:16 who say they know Jesus is a teacher from God, but are trying to trap Jesus. That Nicodemus comes to Jesus at night does not mean he was embarrassed to be seen with Jesus. Jewish teachers in the first century often gathered in the cool evening to discuss Scripture. Rather than engage Jesus in a crowd (as the Pharisees do in Matthew), Nicodemus comes privately to talk with Jesus in a non-confrontational setting.
There is a difference between Nicodemus who says “we know…” and Jesus’s authoritative statement “I say to you…” It is possible Nicodemus represents a faction of Pharisees who were interested in Jesus as a teacher. It is the case that Jesus’s teaching is close to the Pharisees in many ways and that there were Pharisees who became followers of Jesus after the resurrection (Acts 15:1-2). It is also possible disciples of both Nicodemus and Jesus were presented at the meeting John 3. Therefore Nicodemus is asking on behalf of his group, Jesus is responding as an authority.
Nicodemus is therefore an example of an interested observer, a friendly but ultimately unconvinced witness to Jesus. But he never confesses faith in Jesus. The purpose of the dialogue with Nicodemus is not to condemn all Jews as unbelievers, in fact, it is probably the opposite. Some Jews were interested in Jesus and friendly towards him, even if they failed to understand fully who Jesus was.
This view of Nicodemus is connected to the purpose of the Gospel of John. According to John 20:30-31 John wrote so the reader would believe and make a decision to follow Jesus. The example of Nicodemus is a warning to the reader: one can be friendly toward the claims of Christ without accepting them.
If this was a challenge to the original readers of John, it is especially challenging for modern readers of the Gospel. Jesus is still asking, “What do you want with me?”
Bibliography: R. Bauckham, “Nicodemus and the Gurion Family,” JTS 47 (1996): 1-37.
[A brief post-script: I am aware that Nicodemus is sainted in both Roman Catholic and Orthodox traditions. I do not find anything of historical value in these traditions. It is entirely likely Nicodemus was an older man when he met Jesus, so he may have died of natural causes prior to soon after the resurrection. Thanks for the correction, Jeff!]