The public personality who officially symbolises the state in its legitimacy and unity is known as head of state.
Head of state can be both ceremonial or can have significant powers, in presidential system president is the head of the state and he is also the head of government and has all the executive powers. while in semi-presidential system the head has very limited executive powers. In the parliamentary system whether the president has the executive power or not depends on the model the parliamentary system.
In US the president can supervise the executive branch of the government, preparing budget and submitting it to congress, appointing and removing the executive officials and implementing the policies are some of the duties of the president. As being head of the government he is the chief officer of the executive branch of government and presides over the cabinet. He also appoints cabinet members.
