John connects 2:25 and 3:1 by using the same Greek word (anthrōpos) to refer to all of humanity and then to a specific man (Nicodemus).
Nicodemus had deep religious knowledge. He had also seen what Jesus was doing in Jerusalem (2:13–24). But he had not yet experienced spiritual rebirth (a new life that comes from God).
A Pharisee: See study note on 1:24. The Pharisees were a Jewish group who were careful to obey the law of Moses and their religious traditions.
Nicodemus belonged to this group. He was part of the religious leaders. He was respected for his knowledge of the Jewish law. He likely took pride in his careful obedience and moral purity.