I know nothing about it except from the movie but from what I remember it's like a condition where someone suffers all the traits of Jesus Christ's crucifixion. So they get like holes in their hands and feet and marks on their back from getting whipped. I don't believe in it but it's an interesting idea.
actually it aint a well documented phenomenon, many think it is just a fake. More catholic thing than a protestant one, you also has the weeping Madonna(Mary) images, portraits and small sculptures of jesus mother supposedly weeping tears of blood. even the Vatican is highly suspicious toward these events