When corporations get big enough, they usually have a layer of managers at the very top whose boss is the CEO. Most of the time, each of the managers in that layer is responsible for a specific technical function in the corporation and has their own employees to help them to carry out that function. These managers are called “senior executives” and often have the word “chief” and “officer” in their title, just like the CEO, with the word in between being the name of their function, like “Chief Financial Officer” or “Chief Tarantula Handling Officer,” AKA the CTHO.