An act is a specific operation of a being which results in a change in the ontic state. Or in more common parlance: An act is an operation which results in a change in reality. An act instantiates change.
Since in human acts, the will effects the cause of instantiation, the effects of such acts are attributable to will. Hence the person who initiates an act is the originator of it and thus responsible for it.
If the change effected is a result of the operation of the Will, it is voluntary, otherwise it is involuntary. Furthermore, voluntary actions seek to instantiate a desired ontic state, this state being the object of the act.
The intent on the other hand is the state of reality which the intellect seeks to ultimately bring about; the ontic state which it desires, its' intended object.
Intent is realised through act or acts. However this does not mean that what is instantiated is what is intended. Indeed there may be several acts which may need to be done in order to achieve the intended state.
It appears then that the acting person has two types of motive objects. The object that we directly bring about through an act, the instantional object and the the state of affairs we wish ultimately achieved, the intentional object.
When morally considering actions a consideration of the both the instantional and intentional objects must be made in order to correctly consider the act. For an act to be good both the instantional object and intentional object must be good.
Of note, the intention of the Will can be instantiated by means outside the operating being. If for instance, we wish a man to be killed and by some other means not connected to ourselves, the man is killed, the will's intention is actuated, even though it has not occurred as a result of a specific action of our will. This is why ill will alone is viewed as moral negative.