What does managing cover?
Scheduling, standards, resources, sequence. Making sure the right work happens in the right order to the right quality.
It is real and it is undervalued by men who think leadership is the only interesting part. A badly managed operation burns out good people no matter how inspiring the man at the front is.
What does leading cover?
Direction, judgment and trust. Deciding what matters, saying the hard thing early, and being the same man on the bad week as on the good one.
It shows up in whether bad news reaches you while it is still cheap. A leader people manage receives a filtered version of reality, which means he is running an operation on a data feed his own team is editing to protect his mood.
Why does the gap catch men out?
Because the promotion is awarded for the first and measured by the second.
A man is made foreman because he was the best hand. Nobody explains that the job has changed entirely, so he keeps doing the work and calls it leading by example, while the decisions nobody else can make pile up behind him.
How do you tell which you are doing?
Ask when somebody last brought you a problem before it became a crisis.
If the answer is a while, that is not a sign things are going well. It is a sign that telling you has a cost, and people have worked out what it is.