By itself, ONOS is little more than an SDN framework that provides a programmatic API into the network that it controls. In other words, while it provides the ability to manipulate the network, it does not have any logic built into it to do so. Such functions are provided in the form of applications, for simple tasks, and use case proofs of concepts (PoCs) for more complex tasks.
An application implements a narrow set of features and interacts with the rest of ONOS through its northbound API. Examples of ONOS applications include network control functions, such as traffic forwarding, and managerial interfaces, like the GUI.
The following are a set of built-in ONOS applications. You can click on each the link to find out the usage of the application.
Use cases are aimed at tackling complex SDN deployment scenarios faced by the members of the ONOS community. Likewise, their implementations tend to be complex, and usually include combinations of applications, drivers, and at times, system core components and specialized APIs.