PeopleSoft HCM Data Regulated using the below setup information.
Business Units
Table Sets
Set ids 
Record Groups
Business Unit Option Defaults
Org Defaults by Permission List

Now we will look at each item and try to understand what they meant to the organization.
Business Unit:

You create business units  to track and report specific business information.For HCM, you mustestablish at least one business unit.
If your organization uses same processing rules , it make sense to have a single business unit; if you use different rules in different companies, countries, or functional areas, you may choose to create multiple business units.

Read further: http://srini-peoplesoft.blogspot.com/2012/05/hcm-data-regulations.html