Layers are the basic building block of this rendering engine. Each layer has a source (eg. a movie) and an "FX Chain" which is a series of image filters that are applied to the video stream being produced by the layer's source. The post-FX chain video stream is then composited in the canvas using the layer's size, position, and composition mode.
Layers are created, inspected, edited, rearranged, deleted, grouped, and generally controlled via the "Layers" tab in the Workspace Inspector.
Clicking on a layer or group in the list of layers will inspect that layer.
Canvas / Main Output
The "Canvas" or "Main Output" is the image VDMX is rendering for output. A canvas has an explicit size, and is treated like a group- all the canvas' sub-layers are composited ("flattened") within the canvas to produce an image which is then run through the canvas' FX chain.
The opacity for the main output can be set using the "MASTER FADER" slider in the Workspace Inspector.
If the layer's components haven't been opened into independent windows they will be displayed in the workspace inspector window, where you can interact with them. If the layer's components have been opened into other windows, their tabs are activated so the components are made visible in your interface.