Is wages payable is an example of an expense?

Well, yes ...but, there are different kinds of expenses: operational expenses, such as a payroll are not the same as, say, capital expenses, such as buying a large piece of equipment. Capital expenses are writable (taken off taxes) while many operational expenses are not (marketing and advertising expenses, for example, are).

-InThree21 (B.A. Business; maybe an MBA could have a better answer!)