Nicodemus was a Pharisee, and subsequent member of the Grand Sanhedrin. Compared to his fellow Pharisees and Sanhedrin members, Nicodemus believed Jesus Christ to be from God. Only him and his associate Joseph of Arimathea were Christians on the Sanhedrin.
Very little is known about Nicodemus's early life. It is known that at one point Nicodemus became one of the Jewish leaders. He likely became a Pharisee before becoming "Israel's Teacher". As "Israel's Teacher" he was probably responsible for all Jewish education from the general public education of the Jewish Canon (most of the Old Testament), all the way to the schools that trained Rabbis, and Lawyers. As the Jewish teacher, he himself would've been one of the most knowledgeable about the Law and Jewish heritage on the entire Ruling Council. This would have made him one of the more prominent members of the council. He also would've taught the public or those trying to become scholars, himself.
Taught by Jesus
During his tenure as the Teacher, he visited Jesus at night. He addressed him as a Rabbi, because he knew he was a teacher from God; since only someone from God could perform His miracles. The usage of this title for Jesus by the Head Educator was an astounding recognition, and lead to Jesus being called a rabbi on several other occasions.
Jesus replied that only those who were born again could see the Kingdom of God. Nicodemus took this literally and did not understand how an old man could re-enter his mother's womb. Jesus responded that he should understand these things if he was born again under the Holy Spirit.
Nicodemus asked for an explanation as he was still confused. Yet, his response was that since he was Israel's Teacher he should understand.
Reverence for Jesus
Nicodemus was probably the only one among the Pharisees who defended Jesus in a private meeting following His appearance at the Feast of Tabernacles. When the Grand Sanhedrin condemned Jesus's claims, Nicodemus reminded the Council that legally they must hear Jesus's testimony before condemning him. He was only met with a harsh response from the Council, who told him to study the prophecies concerning the Messiah to see that He could not come from Galilee (when indeed Jesus was born in Bethlehem according to prophecy, but lived in Nazareth. The Council insultingly said Nicodemus would've had to been from the Roman province of Galilee to believe Jesus was the Messiah.
He later showed up to help Joseph of Arimathea bury Jesus' body following His crucifixion by wrapping it in linen cloths with the mixture of myrrh and aloes that he bought.