Plain English Meaning
A ground station that tells your aircraft two things at once: which direction you are from the station, and how far away you are. With both pieces of information, you know exactly where you are relative to that station.
Full Definition
A ground-based navigation facility that combines a VOR transmitter, which provides magnetic bearing information from the station, with a DME transmitter, which provides slant-range distance information to the station. Together they allow an appropriately equipped aircraft to determine its position as a bearing and distance from a single point on the ground.
Context Anchor
Seen on instrument charts, navigation displays, and that require both guidance and DME distance.