The definition, and the half everyone skips
A skills gap is the difference between the level a role requires and the level a person currently holds. It exists at three scales: one person against their role, a team against the work in front of it, and an organization against where it intends to be in two years.
The half that gets skipped is the required level. Measuring people is visible work and feels like progress. Defining what each role needs is slower, more political, and produces nothing to show at the end of the week, so it gets deferred. The result is a heat map where every red square looks equally alarming and none of them is actionable.
Deciding which gaps to care about
For most roles there are three to five skills that actually gate the work — where being a level short changes what the person can be trusted with. Everything else is useful context. Treating all of it as equally urgent is the fastest way to turn a skills program into a spreadsheet nobody opens.
The practical filter is one question: if this gap closed tomorrow, what would change? When the honest answer is nothing in particular, the gap is real and still not worth a plan. That is not a failure of the measurement. Knowing which gaps to ignore is most of the value.
Closing one
A gap closes through a plan with a named skill, a target level, activities and a date. The date matters more than it seems: an open-ended development goal is indistinguishable from an intention, and intentions do not survive a busy quarter.
Verify at the end rather than assuming. The reason to re-assess after the plan is not bureaucracy — a plan completed and a level moved are different events, and only one of them means the gap actually closed.