Approvers
With Approvers, you can create a list of approvers for a workflow.
Workflow approvers are assigned according to settings of users, roles, and security groups in the User, Role, and Security Group tools. If, for example, you delete a user in the User tool, and you do not delete the assignment to the user in the Approvers tool, the defined workflow cannot identify the user assignment for the workflow and will fail. Ensure careful management and maintenance of workflow approver assignments.
For a full overview of how Approver Groups are used in combination with Task Actions, see here for an end-to-end guide on how to set up a workflow.