State the rules governing reservations and their effects.

The governing code: the Vienna Convention on the Law of Treaties (VCLT), 1969 — the treaty law's codification (in force 1980; largely customary in effect — Nepal among the states applying its rules). Definition (VCLT Article 2(1)(a)): a treaty is "an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation" — the last phrase the essential lesson: treaty, convention, covenant, charter, pact, accord, modus vivendi, exchange of notes — names vary, the legal nature is one: an agreement governed by international law intended to create legal rights and obligations. Types: by parties — bilateral (the 1950 Nepal–India Treaty) vs. multilateral (the UN Charter, UNCLOS); by function — contract-treaties (an exchange: the trade treaty) vs. law-making treaties (general norms: the Geneva Conventions); by openness — closed, open, framework conventions; by form — definitive vs. provisional (modus vivendi); simplified-form agreements (exchange of notes — outside the VCLT's written definition but not outside international law). Importance: treaties are the modern system's primary source (Unit 2), the constitution-makers of international life (the Charter), and the state's daily instrument — Nepal's existence as a treaty- participant: borders, trade, transit, rivers, labour. The legal face of sovereignty's exercise — consent made visible.