The first century of the Christian Era begins (approximately) with the birth of Jesus Christ.  I say "approximately" because it is largely assumed that the birth of Christ was several years earlier than the year zero or one A.D. 

The actual date does not matter.  The important thing is that Jesus was born.  The God of the universe stepped down into human history in a very personal way.  The Eternal Word became flesh.  The Bible says of Jesus that the fullness of deity (all that God is) was somehow contained within Jesus Christ.

Yet the Lord Jesus was also completely human.  He was born on this earth as a male child to a young virgin named Mary.  He grew up as boys did in those days, and became a man. 

At about the age of 30 years, Jesus began His public ministry of teaching, preaching and giving signs to demonstrate who He really was.  Men and women of God recognized the signs because they knew the promises of the ancient Scriptures.

The Old Testament calls Him the Messiah (Anointed One) of God.  Jesus often called Himself the Son of Man.  This is a title God had also given to the prophet Ezekiel.  It had signified Ezekiel's mortality, and in Christ it also signifies that God became a human being in order to die for our sins.

Jesus never claimed to be more or less than what and who He was and is.  He is the Eternal God, the Savior of the world and reconciler of all things, Scripture says, in heaven and earth.  Jesus was the Executer of God's will.  That is, He came and accomplished all that God wanted to do for sin, for death and for salvation.  Jesus Christ healed the eternal breech caused by sin.  And He made forgiveness and salvation truly possible for everyone and anyone.