Plain English Meaning
A way for controllers and pilots to send each other short text messages through the airplane's radio system, instead of talking over the radio. FANS 1/A is the message format, and VDL Mode 2 is the digital radio channel that carries the messages.
Full Definition
A text-based controller-pilot messaging system that uses the FANS 1/A protocol delivered over the VHF Data Link Mode 2 network. It allows ATC and the flight crew to exchange clearances, requests, and reports as digital messages instead of voice radio calls, primarily over continental airspace where VHF coverage exists.
Context Anchor
Seen in advanced and discussions where clearances or may be sent electronically to the .