Petrifaction in mythology and fiction is when someone or something turns into stone. It's like when you play pretend and pretend to turn your friend into a statue by saying "freeze".
In stories and legends, gods or other powerful beings could turn people or creatures into stone as a punishment or for their own amusement. This happened in different mythologies around the world. For example, in Greek mythology, Medusa had snakes for hair and anyone who looked at her eyes would turn to stone.
In fiction, petrifaction can also happen through magical spells or curses. For instance, in Harry Potter, there is a spell called "Petrificus Totalus" which can make someone completely stiff and unable to move. In the Chronicles of Narnia, a character named Jadis has the power to turn her enemies into stone.
Petrifaction is a common trope in stories because it creates a sense of danger and makes the characters feel vulnerable. It's also a way to show the power of mythical or magical beings.