The man, Jesus Christ, was indeed a man. A human being. Yet He was also God. How? Oneness. He was one with the Father.
Let's review how Jesus Himself describes His Oneness with the Father...
John 10:30
30 I and my Father are one. (KJV)
John 10:38
38 But if I do, though ye believe not me, believe the works: that ye may know, and believe, that the Father is in me, and I in him. (KJV)
John 12:45
45 And he that seeth me seeth him that sent me. (KJV)
John 14:7-10
7 If ye had known me, ye should have known my Father also: and from henceforth ye know him, and have seen him.
8 Philip saith unto him, Lord, shew us the Father, and it sufficeth us.
9 Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Shew us the Father?
10 Believest thou not that I am in the Father, and the Father in me? the words that I speak unto you I speak not of myself: but the Father that dwelleth in me, he doeth the works. (KJV)
If you walked the earth with Jesus, you'd get to know Him as a man. He'd teach. He'd laugh. He'd eat. He'd use the restroom. He'd sleep. He'd rest. He'd pray and speak of His Heavenly Father. He'd fast. He'd cry. He'd sweat. He'd bleed. He would seem like an ordinary man. However... at times you'd feel something otherworldly emanating from deep within Him. Something emanating from the very core of His being. Something powerful. Something that has authority over all creation. Something that speaks to the winds... bringing them into obedience. Something that raises the dead and heals all manner of sickness. Something indescribable. You'd sense GOD Himself at the core of Christ's own person. You'd realize that this man is... also God.
However, keep in mind...God did not reside in Christ as a vehicle. God resided in and permeated Christ's very being. A Oneness so complete, so majestic, and so divine that in Christ it can be said that "God became a man"... and that this very same man was "also God".
No other theological view elevates Christ to such an infinite height of majesty and honor. No other religion expresses Christ's true person to such an infinite degree. Most religions merely make Christ a prophet. No... Christ was not just a prophet. Christ was the human tabernacle of God Himself. To deny this imperils the soul... and reduces Christ to being either a lunatic or a liar.
2 Corinthians 5:19
19 To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation. (KJV)