Plain English Meaning
It is the same airport information pilots normally listen to before takeoff or landing, but sent as written text through a data connection instead of being heard over the radio.
Full Definition
A service that delivers the standard ATIS broadcast — current airport weather, active runways, approaches in use, and other essential arrival or departure information — as digital text (and at some locations as a computer-generated voice) rather than relying solely on a controller-recorded voice transmission over a . D-ATIS is delivered through to suitably equipped and is also to and pilots via the at participating airports.