What is the meaning of the legal phrase 'Ratio Decidendi'?

Ratio Decidendi: It is a Latin phrase meaning "the reason" or "the rationale for the decision". The ratio decidendi is "the point in a case that determines the judgement" or "the principle that the case establishes" . It is a legal rule regarding the legal reasoning behind the judgment of the judge. Ratio includes all of the principles a court relies on – be they moral, political, or social – to justify their reasoning for coming to a decision in a case. A ratio is comprised of the legal points made by all the parties to a case.
In the judicial context, it is the reason which is cited for arriving at a decision in a case. Such reason is not the law that is getting attracted in the contemporary case but is the necessary notion which helps the court arrive at a particular decision.