Which component provides vertical guidance to assist in descent during landing?

The glideslope is the component that provides vertical guidance to assist pilots during descent when landing. It is part of the Instrument Landing System (ILS) and helps maintain the correct angle of descent, typically around 3 degrees, allowing the aircraft to approach the runway safely and consistently. By following the glideslope indicator, pilots can ensure they are on the correct flight path for landing, which enhances landing precision and safety.

The other options serve different functionalities related to navigation and approach. For instance, marker beacons provide position information at specific points along the approach but do not offer vertical guidance. The localizer, while essential for determining the lateral position relative to the runway centerline, does not provide vertical descent information. The Tactical Air Navigation System (TACAN) is a navigational aid that gives range and bearing but does not contribute to vertical descent guidance during landings.