Distributed validators are managed within Clusters - the group of operators that were selected to operate them. Clusters are unique to each account and are used for fees payment facilitation and management purposes.
Example of an account with 2 clusters: Cluster #1 manages 3 validators and is operated by operators 1,2,3,4,5,6,7 Cluster #2 manages 1 validator and is operated by operators 1,2,3,4