Person Model

Person Model is an effective way of tracking employee, Contingent Worker and Person Of Interest in the Organization based on the Organizational/Employee Instance, Assignments with (Employee, Contingent Worker) and without (Person Of Interest) job information .

let us understand important Fields from Person Model.
PER_ORG : How a person is related to the organization (EMP - Employee, CWR - Contingent Worker, POI - Person Of Interest)
ORG_INSTANCE_ERN : How Many Employement Instances a person is having in the Organization.Each Employee Instance should have minimum of one Assignment
EMPL_RCD : How Many Job Assignments a person is having for a Employement Instance in the organization.
POI_TYPE : Person Of Interest Type (Un Known, External Trainer ..etc). Base table to store different Types  is PS_POI_TYPE_TBL, which can be configured going through the navigation Set Up HRMS, Foundation Tables, Organization, Person of Interest Type.

let us understand Important Records from Person Model
PS_PERSON : Every person you enter in the system will have one record in PERSON.Contains the ID and a person’s static data (such as birthdate and birthplace).
PS_PERS_DATA_EFFDT : Maintains Personal History.
PS_PER_ORG_INST : Stores Employement Instances (ORG_INSTANCE_ERN) of a person.
PS_PER_ORG_ASGN : Person Organizational With Assignment i.e Job Assignments(EMPL_RCD) for each Employement Instance(ORG_INSTANCE_ERN).Each row is uniquely identified by the EMPLID, ORG_INSTANCE_ERN and EMPL_RCD .
PS_PER_POI_TYPE : Person Organizational With out Assignment. Person organizational relationships that do not require an assignment (i.e. JOB data). Each row is uniquely identified by the EMPLID and the POI_TYPE (the person of interest type).
PS_PS_POI_TYPE_TBL : Person Of Interest Type,  which can be configured going through the navigation Set Up HRMS, Foundation Tables, Organization, Person of Interest Type.
PS_PER_POI_SCR_DT : History record of information directly related to one Person of Interest relationship without a job (PS_PER_POI_TYPE).
PS_PER_POI_SCRTY : Row Level Security Contains the field and values of data that can be used to define data Permission Security Access for relationships.
PS_PER_POI_TRANS : This is the generic transaction history record for persons of interest

let us look at the navigation's used in the Person Model

Create POI Type : Set Up HRMS, Foundation Tables, Organization, Person of Interest Type.
Creating a Person : Workforce Administration, Personal Information, Add a Person and Workforce Administration, Personal Information,Biographical, Add a Person
Adding a New Employee Instance : Workforce Administration,Organizational Relationships, New Employement Worker Instance
Adding a POI : Workforce Administration,Organizational Relationships, Add a POI Relationship.
Person Organizational Summary : Workforce Administration, Person Organizational Summary
PERSONAL_DATA Snapshot Settings: Set Up HRMS , System Administration, Database Processes, PERSONAL_DATA Settings
PERS_REFRESH Process : Set Up HRMS, System Administration, Database Processes, Refresh Personal Data.
HR_PERSDATA For Future Dated Rows : Set Up HRMS, System Administration, Database Processes , Update Personal Data - Future.

PERSONAL_DATA Snapshot Reporting Table
The first is for the related display of the NAME field in the PeopleTools User Profile page (USER_MAINT component) The second is for customer written processes and pages.

I hope all this information is useful for understanding what is Person Model.