When the Revenue Type of a given product is Revenue from Client, you will be able to see one additional column - Income/Payable, in the Product Fee pop-up.
Income can be a service fee charged for the service offered to the client, whereas Payables are the one which collect from the client and need to be paid to the partner or the third party.
For example, for the Visa Processing service, there are normally two fees charged. One is the Registered Migration Agent Service Fee, which is income and the other is Visa Application Fee, which needs to be paid to the Department of Immigration.