Perhaps in your corporate ladder discussions it may be useful to mention unions vs. managers to make the point clearer. Focusing on senior managers vs. executives is a weaker description because most people see that as one unified ladder, and not two separate ladders.

Similarly: What's a corporate executive? I understand that there is a management hierarchy, but why the arbitrary distinction between a senior manager and a junior executive? Aren't those just two rungs on the ladder? In corporate-speak, an executive is called a "decision maker." What a strange term! Isn't a manager or even a lowly "individual contributor" also a decision maker -- at the scope that their own managers allow?

Yes, they are just two rungs on the (same) ladder. In corporate-speak, an executive is usually responsible for an entire function (e.g. marketing, HR, finance, engineering, IT, sales). "Junior executive" is typically an informal title bandied about in corporations with a deep management hierarchy tree. Senior Manager is usually a formal title. The distinction is less clearcut than you believe other than the formal title vs. informal social references.