Diplomacy: This is the practice of conducting negotiations between countries or groups. It's like having a group chat where everyone tries to solve problems without resorting to fighting.
International Relations: This is the study of relationships between countries, including the roles of states, intergovernmental organizations (IGOs), non-governmental organizations (NGOs), and multinational corporations (MNCs). It's like studying all the dynamics in a schoolyard - who hangs out with whom, who has power over others, etc.
National Security: This refers to the security of a nation state from threats. It's like installing an antivirus software on your computer - it protects against external threats that could harm your system.