There are a number of different resources within the Couchbase Server and these resources will require a different URI/RESTful-endpoint in order to perform an operations:
A cluster is a group of one or more nodes; it is a collection of physical resources that are grouped together and provide services and a management interface. A single default cluster exists for every deployment of Couchbase Server. A node, or instance of Couchbase Server, is a member of a cluster. Couchbase Server collects run-time statistics for clusters, maintaining an overall pool-level data view of counters and periodic metrics of the overall system. The Couchbase Management REST API can be used to retrieve historic statistics for a cluster.
A Server node, also known as 'node', is a physical or virtual machine running Couchbase Server. Each node is as a member of a cluster.
A bucket is a logical grouping of data within a cluster. It provides a name space for all the related data in an application; therefore you can use the same key in two different buckets and they are treated as unique items by Couchbase Server.
Couchbase Server collects run-time statistics for buckets, maintaining an overall bucket-level data view of counters and periodic metrics of the overall system. Buckets are categorized by storage type: 1) memcached buckets are for in-memory, RAM-based information, and 2) Couchbase buckets, which are for persisted data.