Panel and Cockpit Terminology
From X-Plane Wiki
A panel is a 2-d image with multiple instruments that is used to create a 2-d simulation of part of a real airplane cockpit.
A cockpit object is a 3-d object (OBJ file) that is used to create a 3-d simulation of an entire real airplane cockpit.
The panel texture is a dynamic texture (a texture created and updated continuously by X-Plane) that is created by drawing a panel and converting it to a texture for use in an object.
A 2-d view is a view that displays one panel, with the camera angle fixed. The user can scroll the panel up, down, left and right if it is larger than the screen, and can tilt the camera down to help with landings.
A '3-d view is a view that displays a cockpit object, where the user has complete freedom to move or rotate the camera in any way desired.
The 2-d panel is the panel that is used when looking forward in a 2-d view. It typically has the plane's main instruments. It is also used to form the panel texture in most cases.
The 3-d panel is a panel that is used to form the panel texture. See the documentation on 3-d panels for more information.
A Panel Background is a single large image that defines the size and appearance of the panel. It does not change during flight.
An Instrument Background is a single image that defines the non-moving part of an instrument. It is "burned in" to the panel background during panel load.
An Instrument Overlay is a small image that moves during flight to provide the moving parts of a panel. Instruments can have up to four overlay layers.