What does the "Executive" in "Executive Summary" mean?

Solution 1:

An executive summary is a summary of a report that provides sufficient information to allow senior management to make effective decisions without having to the read the entire report. In effect, the contents of the report provides supporting evidence for the executive summary.

So, executive means senior manager in this case.

Solution 2:

For the fellow translators who came here looking for guidance, my suggestion is to treat it as if it were just a summary, main points, key points, at a glance summary, boiling down, gist, essence. Ask yourself "what's the word that I would use to describe something that recounts all the key facts and provides an outlook of reasoning and the conclusion."