As far as I know, there is no such thing as High Level Project Charter that is only dedicated to senior executives, since the project charter is essentially targeted at senior executives (so why create another, shorter one which is also targeted at senior executives).
I don't know where you have read the term, but it just doesn't exist, a project charter is always the same, and consists of the following:
- Vision Statement
- Problem Statement
- Objective Statement
- Project scope (what's in the scope and what's out of the scope of the project).
- The Risks
- The Stakeholders (stakeholder map)