Explain the difference if any, in between 'Res Judicata' and 'Res Sub-Judice'.

The Rule of Res Sub Judice relates to a matter which is pending judicial enquiry while Res Judicata relates to a matter adjudicated upon or a matter on which judgement has been pronounced. Res Sub Judice bars the trial of a suit in which the matter directly or substantially is pending adjudication in a previous suit, whereas rule of res judicata bars the trial of a suit of an issue in which the matter directly and substantially in issue has already been adjudicated upon in a previous suit between the same parties under the same title. Res Judicata arises out of considerations of public policy viz., that there should be an end to litigation on the same matter. Res-Judicata presumes conclusively the truth of the former decision and ousts the jurisdiction of the Court to try the case. It is however essential that the matter directly and substantially in issue must be the same as in the former suit and not matters collaterally or incidentally in issue.