Api vs ComputeServiceContext

[Bk Lau]

I'm a little confused by examples per jcloud 1.6.1

 NovaApi nova = ContextBuilder.newBuilder(provider)
                .endpoint("http://172.16.0.1:5000/v2.0/";)
                .credentials(identity, password)
                .buildApi(NovaApi.class);

          versus

 ComputeServiceContext context=ContextBuilder.newBuilder(provider)
             .endpoint("http://172.16.0.1:5000/v2.0/";)
.credentials(identity, password)
.buildView(ComputeServiceContext.class);


So which one to use?