The Schematic view is the looking glass into your scene.
Use it to add new fixtures, configure their properties such as DMX channels, OSC output addreses, grouping.
Use the top-left button to cycle through various camera angles.
The view is consisted of various layers, many of which can be disabled individually. Refer to the Schematic view part of Controls to learn the hotkeys.
Pressing I reveals the configuration. O and P then switch between property and position gizmos.
You can configure a backdrop to be shown in the view. This way you can use an image based floorplan for reference, or just display your favorite cat picture.