Election is the formal process of selecting a person for public office or of accepting or rejecting a political proposition by voting. It is important to distinguish between the form and the substance of elections. In some cases, electoral forms are present but the substance of an election is missing, as when voters do not have a free and genuine choice between at least two alternatives. Most countries hold elections in at least the formal sense, but in many of them the elections are not competitive (e.g., all but one party may be forbidden to contest) or the electoral situation is in other respects highly compromised.
Methods of election
An election is the occasion or the means by which the qualified voters make a choice among two or more candidates for the seat in legislature or some public office. It is of two kinds, direct and indirect.
Direct election is a term describing a system of choosing political officeholders in which the voters directly cast ballots for the person, persons or political party that they desire to see elected. The method by which the winner or winners of a direct election are chosen depends upon the electoral system used. The most commonly used systems are the plurality system and the two round systems for single winner elections, such as a presidential election, and party-list proportional representation for the election of a legislature.
Examples of directly elected bodies are the European Parliament and the United States Senate (since 1917).
Indirect election is a process in which voters in an election do not actually choose between candidates for an office but rather elect persons who will then make the choice. It is one of the oldest forms of elections and is still used today for many upper houses and presidents. This process is also used in many union elections and sometimes in professional, civic, and fraternal organizations.
Theory of the separation of powers
Since the ancient day of Aristotle, political writers have recognized the threefold distribution of governmental functions or powers. They are 
(1). The law making or legislature power.   
(2).The law-enforcing or executive power.  
(3). The law adjudicating or judicial power. Each power is exercised by its own department or organ of government.

Montesquieu theory
Montesquieu explained his theory in this word: “in every government there are three sorts of power: Legislative, Executive and judicial. The liberty of individual required that neither all these powers nor any two of them should be placed in the hands of one men or one body of men. 
(1).When the legislative and executive powers are united in the same person or body , there can be no liberty, because apprehensions may arise that the king, who is also law maker, might  make and enforce the laws in a tyrannical manner. 
(2).If the judicial power is joined with the legislative , the life and liberty of the subject will be exposed to arbitrary control, for the judge would then be the legislator. 
(3). Where the judicial power joined to the executive power, the judge might behave violence and oppression. 
(4). There would be an end of everything if the same man or the same body, whether of the nobles or of the people, were to exercise those three powers, that of enacting laws, that of enforcing them and of trying the cases of individuals