Who is Tituba from I, Tituba, Black Witch of Salem and what is their importance?

Tituba is the book's central character, its protagonist and narrator. Her story is at least partly based on the life of an actual person - a black servant named Tituba appears in transcripts and court records made at the time of the legendary Salem Witch Trials. Another interpretation of the life of this character appears in the well known play "The Crucible".