Need some help on understanding passing input variable values

I have the following query, need help on understanding the placeholder,

procview expects two input parameter values and how does the values get in, here i just see "Employee" and "ROLE".

Is it not required to pass a value straight away, one single value when calling procview?. i see employee if "employee" is a table, are the values getting in on a row by row basis dynamically from employee and role table?

SELECT * FROM ProcView WITH PARAMETERS

('placeholder'=('$$lt_employee$$','EMPLOYEE'),

'placeholder'=('$$lt_role$$','ROLE'));

Thanksa lot for the helpful info.