What does it mean to be a CTO at a younger company and how does that evolve as the startup matures?

In addition to CTO, would be interested in the entire CxO suite!!

Well, at a young startup, being a CTO means you're the guy who writes code all day, if there's nobody else to do it. 

The thing about being CTO of a startup is if the startup is growing, which hopefully it is, it means your job description changes basically every year. The first year or two your job is probably to just write code all day long. Maybe, in the second year, your job is to do that and also do some sales meetings, and also do some investor pitches. Then hopefully you raise money and then your job becomes, about hiring other engineers to work on this thing with you. And then your job likely switches to being a full time engineer recruiter. That's likely to be your job in years two and three. As you hire more people, it just keeps changing. At a certain point your job becomes managing a small team of engineers, then maybe you get large enough that you actually promote some people into being managers themselves, and then your job is to manage the managers. Recruiting probably stays your job for a long time, but most likely after a certain point you hire recruiters, so now you're not only doing the recruitment, you're managing a whole recruiting effort.

One interesting thing is that as the company gets larger, your job keeps increasing in abstraction. We keep getting less involved in details and more involved in helping other people do the details, and that's often hard for a lot of CTOs. I know it was really hard for me.