It is true that the idea of power sharing emerged in opposition to the notions of undivided political power. Traditionall, it was believed that power should be concentrated in one hands because if power is divided then it would be difficult to take rapid decisions and apply them. But the development of the concept of democracy has changed this notion of power concentration in one hands. This is so because democracy believes in distribution of power among people as people are the source of authority. Power can be divided among the various organs of the government, two sets of the government, hat is central and the state, community government etc. Moreover, concentration of power in one hands leads to revolution and war in the long run and breaks the unity of the nation.
Horizontal distribution of power allows different organs of government placed at the same level to exercise different powers. Such a separation ensures that none of the organs can exercise unlimited power. Each organ checks the others. This results in a balance of power among various institutions. For example, ministers and government officials exercise power, they are responsible to the Parliament or State Assemblies. Similarly, judges can check the functioning of executive or laws made by the legislatures. This arrangement is called a system of checks and balances.
Power shared among governments at provincial or regional level is called as vertical form of power sharing. Such a general government for the entire country is usually called federal government. In India, we refer to it as the Central or Union Government. The governments at the provincial or regional level are called by different names in different countries. In India, we call them State Governments. State Governments and Central Government have their distinct areas to exercise power.