Orion/Documentation/Developer Guide/Plugging into the settings page
Orion plugins can define settings. A setting defines some persistent information that is provided to one of the plugins's services. Defined settings appear on Orion's Settings page, and their values can be changed using an automatically-generated UI. Each setting has a unique identifier called a PID (persistent identifier), as well as metatype information. The metatype defines the "shape" of the setting, specifically what named properties - comprise the setting and what data type they have (string, number, etc).
Contributes a setting.