Plain English Meaning

What the ILS does for the pilot: it shows the airplane exactly where it is in relation to the runway, both side-to-side and up-and-down, so the pilot can fly a steady descent to the runway when they can't see it through clouds or weather.

Full Definition

The role the Instrument Landing System plays in guiding an aircraft to a runway during an instrument approach. The ILS provides the pilot with precise lateral guidance (left/right of runway centerline) via the localizer and vertical guidance (above/below the proper descent path) via the glideslope, allowing a stabilized descent to a near the in .