The holy and righteous Nicodemus was a Pharisee who came to hear the Lord by night. After the Crucifixion, he acted as one of the Holy Myrrhbearers. Because of this, he is commemorated on the Sunday of Myrrh-bearing Women, two weeks after Pascha.
In the Gospel of John, he appears three times. The first is the aforementioned encounter, where he visits Jesus in the dead of the night (in order to avoid persecution by the Sanhedrin, the Jewish temple leaders, of which he was a member) to listen to his teachings (John 3:1-21). This meeting, a poignant scene in the Gospel, is where Jesus tells Nicodemus that one must be "born again" in order to enter into the Kingdom of God. The second appearance is in John 7:45-51, where he states the law concerning the arrest of Jesus at the Feast of Booths. Finally, his last appearance is after the Crucifixion where he assists the Noble Joseph in recovering Jesus' body and preparing it for burial (John 19:39-42).
Not much is known outside of John's Gospel regarding the life of St. Nicodemus after the Resurrection. Church tradition states that he was possibly martyred sometime during the 1st Century AD.