LANC is a terminal on Sony as well as other manufacturers' camcorders which enables other accessories like Tripods with a control handle to control the camera with a wire connected to a LANC port without dealing with buttons on the camera itself. It is also available on many still cameras, where it is called ACC (the DSC-xxxx series of cameras).
The bi-directional protocol is made up of 8 (8-bit) bytes, usually clocked by the camera at 9600 bit/s. Each frame of bytes occurs in sync with the beginning of each video frame (NTSC or PAL). The physical connector is either a 5-pin mini-DIN connector and jack or a 2.5mm 3-conductor phone jack and plug (TRS connector).
In newer Sony digital Handycam(R) camcorders with 10-pin multi-A/V remote terminal jacks, LANC is available, but not directly accessible without making a custom/home-made adapter cable or a pre-made cable by Sony Part# J-6082-535-A. Sony RM-AV2 Remote Commander is an example of a LANC controller which plugs into the Sony 10-pin multi-A/V remote terminal jack.
Sony "Control-S" is a similar interface, but it is uni-directional providing control-only, and not feedback from the device being controlled.