The seven-pointed star is the symbol of the Faith of the Seven.
The Faith of the Seven was brought to Westeros by the Andals who conquered the South, and made it the predominant religion. Some Andal warriors cut the seven pointed star into their flesh. They considered worship of the Old Gods sacriligious, and cut down and burned most of the weirwood trees in the South.
The Crone is the face of fate. She is often represented carrying a lantern.
It is said that she let the first raven into the world, when she peered through the door of death.
Followers of the Faith of the Seven, implore her to grant them wisdom.
Melisandre is a priestess of the faith of R'hllor, a follower of the Lord of Light.
She is from the eastern city of Asshai, but has joined forces with Stannis Baratheon, and has become an influential advisor to him.