Hi Koti. Both are built-in processes that don't really require any configuration, and they are similar so I understand any confusion that there may be.
Cluster controller you can think of as the overarching monitoring of the system and if there are issues, then I think it will send out emails of up and down status for each of the processes. Also, when you move around processes between nodes in a cluster, I think this is the process that handles the associated work.
Coordination service comes into play more so for high availability (minimum of 3 nodes) clusters. It's built on top of open source Apache zookeeper and it ensures that there is a quorum of available nodes, and if not it attempts to initiate work to failover the repository and data engine as needed.
Cluster controller - Tableau Server Processes - Tableau
Coordination service - Tableau Server Coordination Service - Tableau