Pools and swimlanes are elements of symbol notations that can be used via the symbol library (FLOW, BPMN).
Swimlane
So-called “swimlanes” are often found in flowchart and BPMN diagrams.
They are used to represent the 'ownership change' of subprocesses, groups or systems.
The lane elements are Container Elements holding the elements and keeping them in position.
Pools
The swimlane concept consists of a pool (containing the 'ownership areas' e.g. organization, department or role) and the actual swimlanes (containing the activities).
If a lane is selected, buttons are provided on the right-hand side to add lanes above or below or to split the lane.
The order of the swimlanes can be changed by using the arrows.