In most examples, we are writing a route which represents the flow of your integration solution. Those routes are usually defined in a RouteBuilder. Most of the keywords are dealing with the Camel Message, unless specified as body specific (for example, process deals with a Camel Message and processBody deals with the body of the Camel Message).
Warning
In the Message interface, its body is represented as an Option[T] to handle the nullable case. Thus, the keywords, such as process, which handles a Message should be aware of this point. The keywords, such as processBody, which handles directly the Message body do not have to care about that.