Swim Lanes models divide a screen or page into multiple parallel lines or lanes. The lanes are generally represented as long vertical or horizontal rectangles or sometimes‐simple lines or bars.
Each of these lanes is defined as a specific organization unit or a business role that a person plays in performing the work. The work moves from activity to activity following the path of the flow from business unit to business unit or from role to role.
By showing the flow from lane (role/ organization) to lane, swim lanes help identify hand‐offs in a process.
Source: Guide to the Business Process Management Body of Knowledge – ABPMP BPM CBOK V3.0.