A UN resolution is a formal expression of the opinion or will of a particular body (General Assembly, Security Council or Economic and Social Council) that usually requires a majority vote. It may also include an annex with additional texts and/or amendments. Resolutions and decisions are often issued as individual documents, but they can also be included in annual or sessional compilations of the bodies.
Security Council resolutions are more “worth something” than General Assembly ones, because they can be enforced, particularly if adopted under Chapter VII of the Charter, which allows for sanctions and military action. Nevertheless, it is possible for states to ignore them, and they do. The use of the veto loomed large in 2024’s Israel-Gaza conflict, as Russia and China swung it to block resolutions condemning Israeli settlement expansion. The use of the veto dates back to World War II, when the major Allied powers sought a mechanism for enforcing international law. This resulted in the veto being included in the UN Charter at the 1944 Dumbarton Oaks and 1945 Yalta conferences. It has remained a central feature of the United Nations since then, despite criticisms by humanitarian groups and others.