party that hold majority during general election
The statement, "The parliamentary form of government gives most of the power of government to the executive" (that is, to the executive branch of the government), is in fact generally false. While an executive branch of a parliamentary system may in fact have tremendous freedom to act politically as its particular genius dictates, it nevertheless receives legitimacy from the legislative branch of the government, which retains the power to revoke the power of the executive branch by formal schedule, in identifiable emergency-situations, or otherwise.
Theoretically, the legislative branch of government has more power in a Parliamentary system than in a Presidential system of government.
The state governments have most of the power.
It can be, but not necessarily. A unitary state is simply one where the power is centralized in one place and contrasts with a federation in which power is divided among states/regions and a central government. For example, the UK is a unitary state (for the most part) whereas the US is a federation. A parliamentary form of government simply means that the executive branch/ministers/cabinet are part of the legislative body. Both unitary and federal states can have parliaments. For example, India is a federation with a parliamentary system where as the UK is a unitary state with a parliamentary system.
Prime minister
That's easy! - most British Citizens are eligible to vote in Parliamentary elections, once they are 18. The Political Party that wins the most seats in Parliament will form a Government. The leader of the largest Parliamentary Party (and therefore the leader of the governing Party) becomes PM and head of the Government.
Parliamentary democracy
Under a confederate system of government much of the power is located in the individual states. The lack of a strong system of central government caused the Articles of Confederation for fail in the United States.
Most countries in Europe are parliamentary democracies, including the UK, Netherlands, Ireland, Germany and Austria. France and Russia have a semi-presidential system of government. Europe's only dictatorship is Belorus.
executive
Europe's old form of Government was the Monarchy, but most of them today are democracy
A Parliamentary government is a system of government in which the real executive power is in the hands of a cabinet constituted by members of the legislative body who are individually and collectively responsible the legislature while there is only at the most a nominal chief of state.