The term alter ego is commonly used in literature analysis and comparison...

0 An alter ego (=the opposite side of the personality, counterpart) is a second self, a second personality or persona (=an individual's social facade, the personality that a person projects in public, image) within a person. It was coined (=invented) in the early nineteenth century when schizophrenia (=a serious mental illness in which someone's thoughts and feelings are not based on what is really happening around them) was first described by early psychologists.02br
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00The term alter ego is commonly used in literature analysis and comparison to describe characters who are psychologically identical, or sometimes to describe a character as an alter ego of the author, a fictional character whose behavior, speech or thoughts intentionally represent those of the author.02br
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00The characters Doctor Jekyll and Mister Hyde in Robert Louis Stevenson's thriller Strange Case of Dr Jekyll and Mr Hyde represent an exploration of the concept that good and evil exist within one person, constantly at war. Edward Hyde literally represents the doctor's other self, a psychopathic being (=a living thing, especially a person) unrestrained by the conventions of civilized society, who shares a body with the doctor.02br
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01b00The term and concept also frequently appear in popular fiction, such as in comic books, for the secret identity of a superhero, vigilante 02b00(=someone who illegally punishes criminals and tries to prevent crime, usually because they think the police are not doing this effectively)01b00, crime fighter or villain.02b00 Related concepts include avatar, doppelganger (=a ghostly counterpart of a living person), impersonator (=to assume or act the character of, personate), and split personality.02br
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01span00I couldn't understand the bold part. Please help.02span00 0-