Question: Ask-us-anything-how-to-alias-dashboard-variables-in-grafana-in-sql

I have a requirement similar to what is described with its solution in the article:
My question is about the template variable. The article uses $service_id variable but when I follow it I find out that $service_id is not a variable in the dashboard that I create. I can use $name instead. Could anybody explain why’s the article uses $service_id instead of $name?