What does 'the mystery of incarnation' mean?

Carne means "flesh"

"The Incarnation" means the process whereby Mary gave birth to Jesus without the involvement of a human male.

The Incarnation is God taking human flesh by the power of holy spirit /

God becoming Man (Jesus Christ)

The Incarnation happened 9 months before the birth of Christ.

When Mary said "yes" and the greatest Miracle of all happened, God became man