This is a symbol combining 3 ancient symbols: The menorah, star of David and the fish at the bottom. It is used in messianic (jews that believe in Jesus) circles as well as christian circles to represent the unity of believers in the faith. It is an awesome symbol that represents both jew and gentile one in messiah.
  In scripture it is a picture of unity:
Psalm 122:6; Matthew 18:19; Romans 11:18