It is fair to say that, given you are reading this book, you already have a good idea of what a Chief Technology Officer (CTO) is. Yet, if all readers were to be polled on their definition of a CTO, we would get as many different perspectives as there are readers. Each description, though, is most likely right. This huge variety in interpretation is what makes this role not only challenging but exciting at the same time.
The closest counterparts, Chief Executive Officer (CEO) and Chief Financial Officer (CFO), are well-defined roles, with their areas of responsibility clearly understood: the CEO leads the charge, and the CFO writes the checks! Okay, a little disingenuous, but the point is, these roles are universally accepted, compared to the ambiguity around the CTO role.