Black's Law Dictionary (10th ed. 2014) defines comparative law as "The scholarly study of the similarities and differences between the legal systems of different jurisdictions, such as between civil-law and common-law countries." In other words, particular rules or aspects of the law or legal system of various jurisdictions are compared and contrasted
Foreign law is the national (also referred to as domestic or internal) law of any country other than the United States and usually refers to constitutions, legislation, and cases. Foreign law has no effect outside the foreign jurisdiction, but it may regulate foreign entities within state boundaries.
International law is the law of international organizations, such as the United Nations, and the laws between nations, such as those established by treaty.