the supreme court can declare laws or presidential actions unconstitutional through a process called judicial review

That is correct. Judicial review is the power possessed by the Supreme Court (and other federal and state courts) to examine the constitutionality of laws or actions taken by the executive branch, including the President. If the court finds that a law or action is unconstitutional, it can declare it as such, rendering it invalid and unenforceable. This power is derived from the principle of checks and balances, which allows the court to ensure that no branch of government exceeds its constitutional authority.