It depends on the country. In some countries, the same person is the Head of State & Head of Government (United States, Brazil, etc). In some countries, the Head of Government holds the power while the Head of State is a figurehead (United Kingdom, Israel, etc). In some states, the Head of State is the most powerful figure, while the Head of Government still holds some power (France, Syria, etc). Oftentimes, the role does not matter and it just comes down to who is in the seat. It doesn't matter if it's President Putin or Prime Minister Putin.