This workflow loops on a list of unique values, in this case on a list of countries. The goal of the workflow is to identify the countries included in the file sales.csv and calculate some statistics on sold products for each one of these countries. First we read the data and we isolate the list of unique countries using a GroupBy node with group column "country" and no aggregation parameters. Then we pass the list of countries to a Table Row to Variable Loop Start node. This node takes the country one at a time and passes it to the loop body. In the loop body the data about the current country are isolated and statistics on sold products is calculated. Finally stats numbers are collected in the Loop End (2 ports) node.
This is a companion discussion topic for the original entry at https://kni.me/w/UD4ijYFV4tmPEL1G