Short answers, pulled from the story.
International relations became a formal academic discipline in 1919, when the Woodrow Wilson Chair was established at Aberystwyth University in Wales, the first professorship dedicated to the field. The chair was endowed by David Davies and first held by Alfred Eckhard Zimmern.
Realism holds that the international system is an anarchy in which states pursue military and economic power to ensure their own survival, treating international organizations as tools states use for their own ends. Liberalism argues that states are institutionally constrained by international organizations and economically interdependent, making cooperation rather than conflict the rational strategy.
In a 1992 article in International Organization, Alexander Wendt argued that the anarchic structure realists treat as a fixed feature of the international system is actually socially constructed and reproduced by states themselves. His phrase was that anarchy is what states make of it.
The Peace of Westphalia, signed in 1648, is associated with the establishment of modern sovereign states as the fundamental units of international politics. Many historians of international law also point to the Treaty of Utrecht of 1713 as the clearer articulation of the principle that sovereigns had no internal equals and no external superiors within their territory.
Dependency theory holds that a set of core developed states exploits weaker periphery states to advance their own prosperity. It is most commonly associated with Marxism and argues that developed states integrate developing ones into the capitalist system through banking, security, and trade agreements as well as through informal channels including financial advisors and multinational corporations.
Polarity refers to the arrangement of power within the international system. During the Cold War the system was bipolar, dominated by the United States and the Soviet Union. The collapse of the Soviet Union in 1991 produced unipolarity, with the United States as the sole superpower. China's emergence as the world's second-largest economy in 2010 has prompted ongoing debate about whether that unipolar structure will persist.