What is meant by legitimate govt and why its important outcome of democracy?I m really confused so please explain is throughly.

Legitimate government means a government which emerges through a due process of law. In a democracy, it means that the government is formed once a party wins an election and satisfies all the rules laid down by the Constitution for forming a government. In contrast, if a dictator takes over power, then that is an illegitimate government as it is not in accordance with the Constitution. 

A legitimate government is an important outcome of a democracy because democracy through the will of the people as expressed in an election confers legitimacy to a government.