In Functional org  entire organizational activities are divided into specific functions such as operations, marketing, finance, personal relations, product development etc. So it has some complexity of  administrative organization compared to the other two . Each functional area is put under manager of functional specialists and he has got the authority to give all decisions regarding the function whenever the function is performed.

So your project may or may not involve different functional departments. For eg. Its possible that for product development, the requirements may be given by sales department , since they are interfacing with customer, Tested by Quality team, Built by development team , security tested by Security department and so on.