Marker Interfaces
A marker interface is an empty interface with no attributes, events, or methods. A marker
interface is used to enable specific usage for a component in an app.
For example, a component that implements the force:appHostable interface can be used as a custom tab in Lightning Experience or the Salesforce mobile app.
In JavaScript, you can determine if a component implements an interface by using myCmp.isInstanceOf("mynamespace:myinterface").