The Base category of HL7® FHIR® resources includes Individuals, Entities, Workflow, and Management.
Individuals resources are used to describe the people that participate in healthcare. This includes patient, practitioners, and others that are related in some way to a patient. This does not include the Person resource, which is used to index a real world person providing a means to identify the same person across different healthcare organizations.
Entities are used to track, relate, and locate things and people across the healthcare spectrum. They include things like Location, but also the Person resource. The Person resource is used to index a real world person providing a means to identify the same person across different healthcare organizations and roles.
Workflow resources focus on the coordination of activities within and across systems. Primarily they are used to manage and schedule care given in the healthcare setting. Though this does include things like patient appointments, it also includes the resources used to schedule resources such as rooms and devices.
Management resources are used to manage the lifecycle of patients within the healthcare setting.