The "manifestation" of God is the revelation to the nations of God's Will, His Laws, His Commandments, which are proclaimed by all the Messengers of God: Patriarchs, Prophets, Jesus Christ and His Apostles. 
The "appearing" of Jesus Christ is man's realization, acceptance, fulfillment, and proclamation of the Teachings of Jesus Christ and His holy way of life.
"Apparition" is also a symbol of man's spiritual epiphany in understanding, realizing and accepting the Will of God, His Commandments proclaimed by the Patriarchs, the Prophets and Jesus Christ.