Your VMware Cloud on AWS SDDC initially includes a single cluster, named Cluster-1, that contains two resource pools. Additional clusters that you create are numbered sequentially, Cluster-2, Cluster-3, and so on.

A vSphere cluster organizes and manages all CPU, memory, and storage resources of a set of hosts. Each cluster supports multiple resource pools. A resource pool is logical abstraction for flexible management of resources. Resource pools can be grouped into hierarchies and used to hierarchically partition available CPU and memory resources. See Managing Resource Pools in the vSphere Product Documentation more information.

On creation, Cluster-1 has two predefined resource pools. They share the same physical hardware but are dedicated to different uses.
This resource pool is always created in Cluster-1, and never consumes resources from other clusters. Resources in this pool are reserved for management VMs so that they can operate without consuming resources from the Compute-ResourcePool. For a summary of resources consumed by management VMs, see the SDDC vCPUs and SDDC RAM values in VMware Configuration Maximums.
This resource pool is initially created in Cluster-1. By default, all workload virtual machines are created in the top-level (root) Compute-ResourcePool. Each additional cluster that you create starts with its own top-level Compute-ResourcePool. You can create child resource pools of any Compute-ResourcePool to give you more control over fine-grained allocation of compute resources.