If you are the CTO and have a VPE, the VP typically tends to focus inwards, while the CTO has the luxury to care more about outwards topics - strategy, vision, investor relations, business relations etc. The VP focuses on processes, projects, coding standards etc.
It's similar between CEO and COO. If you have a COO you trust, as a CEO you can focus much more outwards about high level issues (strategy, investors, business partners etc). The COO makes sure that the business runs smoothly (hiring, processes, quality of service etc).