The second person in God, the Son, became human Himself: was born into the world as an actual man -- a real man of a particular height, with hair of a particular color, speaking a particular language, weighing so many stone. The eternal being, who knows everything and who created the whole universe, became not only a man but (before that) a baby, and before that a fetus inside a woman's body. If you want to get the hang of it, think how you would like to become a slug or a crab.
The result of this was that you now had one man who really was what all men were intended to be: one man in whom created life, derived from His mother, allowed itself to be completely and perfectly turned into the begotten life. The natural human creature in Him was taken up fully into the divine Son. Thus in one instance humanity had, so to speak, arrived: had passed into the life of Christ. And because the whole difficulty for us is that the natural life has to be, in a sense, "killed", He chose an earthly career that involved the killing of His human desires at every turn -- poverty, misunderstanding from His own family, betrayal by one of His intimate friends, being jeered at and manhandled by the police, and execution by torture. And then, after being thus killed -- killed every day in a sense -- the human creature in Him, because it was united to the divine Son, came to life again. The Man in Christ rose again: not only the God. That is the whole point. For the first time we saw a real man.
Jesus did not masquerade as a man, He was a man.