What’s Up With the Title?
This one's not too tough. The title lets us know that the story we're about to read is a gospel (see "Genre" for more on that) and that it was written by someone named John. Oh, except that this gospel was almost certainly not written by any one person named John. Want more? Check out our discussion in "Theological Point of View."
P.S. Remember, there isn't a standard title for this gospel. You might see it called various things like "The Gospel According to St. John," "The Gospel of John," or, more simply, just "John."