Tactical Voting 

• Also known as strategic voting, this refers to the act of voting for a particular candidate or political party not because the voter necessarily supports them but because she wants to prevent some other party or candidate from winning.
• For example, a voter who prefers a leftist candidate would vote for a centrist candidate in order to prevent a right-wing candidate from winning because the leftist candidate is weak in that constituency.

Proportional Representation

• This refers to an electoral system in which the distribution of seats corresponds closely with the proportion of the total votes cast for each party.
• This is a more complicated but representative system than the first-past-the-post (FPTP) system, which is used in India.
• If a party gets 40% of the total votes, for example, a perfectly proportional system would allow it to get 40% of the seats. Some countries used a combination of the proportional representation system and the FPTP system.

Source:TH