The task of the referee is to evaluate in a timely manner a paper for publication in a specific journal or conference proceedings.
Reference: The Task of the Referee by Prof. Alan Jay Smith, University of California.
"This involves determining if the work presented is correct, if the problem studied and the results obtained are new and significant, if the quality of the presentation is satisfactory or can be made so, and what revisions and changes to the paper are necessary and/or desirable. The evaluation must be with regard to the coverage and degree of selectivity of the specific publication."