Could anybody help me to understand these two tables? 

create table company_emp_tab
(
  company     varchar2(20) not null,
  employee_id varchar2(11) not null,
  person_id   varchar2(20) not null,
  ...
)
primary key (company, employee_id)

create table company_person_tab
(
  company_id             varchar2(20) not null,
  emp_no                 varchar2(11) not null,
  operator               varchar2(30) not null,
  ...
)
primary key (company_id, emp_no)

I see that company_emp_tab belongs to the ENTERP module, while company_person_tab belongs to the PERSON module.

Is the operator = user_id?

The name company_person_tab suggests it is meant to store information about a person, but it seems to store employee data instead.