The Paths section of an API lists the operations available within that API. It can be colapsed to save space on the page. Click on Paths to colapse or expand the section. If it is still not visible try to refresh in a few minutes. Older versions of Internet Explorer may encounter problems viewing APIs.
When you add an application you are provided with a client ID and client secret for the application. You must supply the client ID when you call an API that requires you to identify your application by using a client ID, or a client ID and client secret.
To register an application click on Apps in the main menu and then click on the 'Register an application' link. Once you have provided an application name, description, etc you will be shown your application client ID and client secret.
A plan is collection of API resources or subsets of resources from one or more API. A plan can contain a mixture of HTTP GET, PUT, POST, and DELETE verbs from different APIs or it can contain all the GET verbs from various APIs. A plan can have a common rate limit for all the resources or each resource can have a different rate limit. Rate limits specify how many requests an application is allowed to make during a specified time interval.