Hi Vin,
Use PE04 to find help of operations.
For example in first line it says VARST FREE VARST is operation and you can call it with different parameters. In this case I call FREE as it's second part.
VARSTFREE check if this is working day for EE or not. You see the description: SCHEDULED DAY OFF?
If the result in NOT mean EE has to be in work then in next line it checks VARST PRSNT means if EE is present at work or not and so on.
Go PE04 and put VARST and have a look its documentation (blue button on toolbar)
Regards,
Omid