Dulcinea del Toboso is not a real person, and she never appears in all of the books. However, this lovely woman exists in mind and fantasy of the main hero. It is the main motivator of everything he does. Her real name was Aldonza Lorenzo, but this didn’t sound romantic for the main hero’s idea of knighthood and glory, and that’s why he renamed her in Dulcinea del Toboso since Toboso is the name of the town she lives in. In the book, she is described as a very delicate, kind and charming lady.
Dulcinea del Toboso in the Essays