Final answer:
In Customer Success Management (CSM), a customer who sells and supports other customers is known as a Partner. This type of customer typically adds value or supports the products or services they are reselling.
Step-by-step explanation:
In Customer Success Management (CSM), a customer who sells and supports one or more other customers is commonly known as a Partner. This typically refers to a business entity that, in addition to purchasing products or services, also extends those services to others, adding value or providing support in the process. In other contexts, such an entity might also be referred to as a reseller, distributor, or value-added reseller (VAR).