No matter what, it is a procedure in which a baby, rather than being born vaginally, is surgically extracted (removed) from the uterus.
As the name "Cesarian" suggests, this is not exactly a new procedure. It was done in ancient civilizations upon the death of a pregnant woman who was near full term in order to salvage the baby. Julius Caesar (or one of his predecessors) was born by this procedure.
The term "section" in surgery refers to the division of tissue. What is being divided here is the abdominal wall of the mother as well as the wall of the uterus in order to extract the baby.
In Shakespeare's Macbeth the Witches' prophecy was that "...none of woman born/ Shall harm Macbeth" (IV.i). Unfortunately for Macbeth, the Scottish nobleman Macduff was "from his mother's womb/ Untimely ripped," and thus not naturally "born of woman" (V.vii). Macduff was the only agent capable of destroying Macbeth. He killed Macbeth in battle.