In the system, a “person” is a representation of a person from the real world, a human resource relevant to the organization’s business – an employee, supplier, intern, etc. These people may need to be registered in the system for various reasons. They may need to access the system to perform certain activities, and for this their identify must be verified (authentication), while other people may interact with the system without needing to be authenticated (they may simply receive notification e-mails, or answer interviews).
For details on creating people, see Chapter 2: Organization -> People -> Manage People or for details on how to integrate an external directory service see Chapter 17: Administration -> Integrations -> Integration Tasks -> Creating a Task to Integrate with an LDAP.