Internal and external proxy services in the service bus.

An External Proxy Service is a service which is exposed to the world outside the enterprise service bus. They would have an endpoint which a consumer sitting outside the OSB can invoke. Invocation of an external proxy service does not depend on a service invoking it from within the service bus.
An external proxy service is normally configured to use the http/jms transport configuration and have an endpoint.

An Internal(Local) Proxy Service is a service which is not exposed to the world outside the enterprise service bus. They do not have an endpoint which a consumer sitting outside the OSB can invoke.
In order to invoke a internal proxy service the consumer will have to invoke an external proxy service which in turn will have to route it to the internal service.
An internal proxy service will have to configured to use the local transport configuration and thus would not have an endpoint.
Local proxy services do not have an URI. However, there are no constraints on the service and interface types supported by local transport proxy services. The one exception is that SAML is only supported in a pass through scenario.

Limitations

The limitations of the local transport are:

    * You can invoke the proxy service using the local transport only from another proxy service.
    * The proxy services using the local transport cannot be published to the UDDI.
    * A local transport proxy service cannot process inbound WS-Security SAML tokens.

Internal proxies are more like private services to the OSB which you do don’t want to expose to the world outside the bus.
On the other hand External proxies are more like public services.

Both have their own importance depending on what you want to use them for.
For more information refer to the official documentation here