Think about the last time you visited a supermarket. 

You probably saw:

• the "Grandmother" - with her list, walks each aisle getting what she needs - that is the DEFAULT
• the "Wife, also shopping for her Aunt" - with her list AND her Aunt's, walks each aisle getting what they both need - that is BATCH
• the "Husband and Wife" - they decide to split the list - cold things and regular groceries - that is WAVE
• the "Employee" - they are shopping for multiple customers - so they split their cart/trolley into sections - that is CLUSTER