Apache camel is very cool in some sense that, it might be working like spring integration, or more as a enterprise integration pattern.
If with spring, it starts from camel context. Like spring application context. Within the camel context, the route builder should be specified. Key method within this route builder is the configure method.
Normal pattern is like from(one endpoint).bean ref(bean name, method).to(another endpoint) within the configure method.
The endpoint can be mq, timer, ejb etc.
The route builder will listen to the queue, for example, then upon any message comes, it will invoke the method of the bean, and possibly would send to another queue for example.