revenue

Hi My Dear Tutor, I have a question.

is the performance obligation amount is the same as the agreed value of work completed and billed to date?

Also sometimes it shows

he agreed value of work completed and billed to date—x
less cash received ————————————————(x)
equal receivable

and sometimes even cash received has been given simultaneously work certified too but we deduct work certified amount?

performance obligation satised over time–x

less work certified ——————————(x)

equal receivable

Need explanation

thanks in advance.