Explanation/Reference:
SQL Server Resource Governor is a feature than you can use to manage SQL Server workload and system resource consumption. Resource Governor enables you to specify limits on the amount of CPU, physical IO, and memory that incoming application requests can use.
The following three concepts are fundamental to understanding and using Resource Governor:
Resource pools. A resource pool, represents the physical resources of the server.

Workload groups. A workload group serves as a container for session requests that have similar

classification criteria.
Classification. The Classification process assigns incoming sessions to a workload group based on the

characteristics of the session. You can tailor the classification logic by writing a user-defined function, called a classifier function. Resource Governor also supports a classifier user-defined function for implementing classification rules.
References: https://docs.microsoft.com/en-us/sql/relational-databases/resource-governor/resource- governor