A Nominal head is the constitutional head of the country who represents the country but does not rule the country.
A Real head is the position of a person who is the head of the government and rules the country.
nominal head : the person who represent our country but do not rule his/ her country, like the president he is representing our country but not ruling it.

real head : the person who leads the government and he even rules his/her country it is like the prime minister who can rule the country.

hope so my answer is useful...........^_^  !!!!