Swim lanes are not exclusive to any particular business processing technique, and can in fact be used with simple flowcharts, activity diagrams, BPMN 2.0 or almost any other process modelling technique. Swim lanes are visual containers that partition a business process diagram horizontally or vertically. They represent different participants, roles, departments, systems, or organisational units involved in the execution of a process. Swim lanes provide clarity and structure to process diagrams by categorising activities based on their performers or responsibilities.
The above is called a 'Pool' this pool has swim lanes, in the above I've depicted vertical swim lanes, but there is nothing wrong with using horizontal lanes. I generally choose vertical ones, because, most mediums have more vertical space than horizontal, not to mention that no one likes reading sideways text, however the following is perfectly legitimate.
Whether the lanes or horizontal or vertical is completely in consequential, the value of the swim lane is two fold, it easily identity's the actor, and segments their contribution to the process.
One thing to keep in mind about the above is that it is very much a contrived example, once could argue that this is in fact multiple business process, that the stock clerk is a variation, etc.
The take away here is simple, Swim lanes segment a process by actor, they represent different participants, roles, departments, systems, or organisational units involved in the execution of a process. They provide a clarity of who does what and at which point during a process.
