In a small company CTO seems more like a cool title than actually a real role.
In large companies, C-suite roles all mean “someone who comes up with company strategy given a particular set of incentives.” E.g.:
• A CEO is the voice of the Board of Directors within the company hierarchy, and—because they can be fired by the Board—is incentivized to strategize in the direction that will give shareholders value and address their demands.
• A COO is ultimately responsible for the company’s operations, both its operational expenses (e.g. product sitting in warehouses depreciating) and operational revenue (liabilities incurred for income unmatched by deliverables); and is on both sides incentivized to strategize in the direction of making the operations pipeline “leaner”—in est, getting other parts of the supply chain to “hold the bag.”
• A CTO (or CIO, depending on the type of company) is ultimately responsible for any IP assets on the balance sheet; and for any expenses that go into producing such IP. As such, they’re incentivized to create and fund R&D efforts (but also to make them lean), and to push to acquire companies with valuable IP (but to be a miser in the M&A negotiations.) They’re also incentivized to find new ways to exploit any technological resources on the balance sheet, in order to increase their liquid value.
• A CPO (Chief Product Officer—not that many stable, large companies have anyone by that name) is ultimately responsible for exploiting developed or acquired IP assets by building operational revenue sources “around” them, and is measured by the new revenue sources they create. This is what a startup’s “business founder” really is, most of the time, except when they’re raising (during which they’re more playing the CEO role.)
I would liken a company’s C-suite to a Congress: it’s a bunch of people with mostly equivalent responsibilities (define top-level strategy and delegate out the execution) but different constituencies driving their beliefs and preferences.
If you’re actually doing anything in your job that a “corporate Congressman” wouldn’t do, then you’re not really in a C-suite role; or, at least, you have multiple roles within the company, and your C-suite role is just a part-time gig.
(I would highly encourage the latter POV: if a technical cofounder is both a CTO and a Head of Engineering, then later they can give away or delegate one of those titles while retaining the other. I say “delegate” because, as a cofounder, they’re a shareholder on the Board, so ultimately they’re “above” whoever the CTO is, through the office of the CEO, even if they don’t personally end up holding any C-suite title in the end.)
I have seen companies that have both. Purposefully before Googling it myself;), my personal experience in such cases CIO would be more business oriented and have a more software/data oriented view; whereas a CTO would be more implementation, technology, infrastructure, enforcement of standards and policies orientation.
Edit, after Googling, other disagree with my experience: CIO is for internal operations, CTO is for external business:
https://www.linkedin.com/pulse/difference-between-cio-cto-ra...
https://www.telegraph.co.uk/business/ready-and-enabled/cio-v...
VP Eng configures engineering's organizational structure, sets processes, and manages engineering managers.
VP Eng doesn't make architectural or technology decisions.
VP Eng is a good hire for many startups that start out with a CTO who isn't a specialist in management (which will be most founding CTOs).