International politics is concerned with the way that nations interact with one another in global contexts. This can include how international organizations like the UN or NATO collaborate and make decisions, but also how shared challenges such as climate change or pandemics are addressed across borders. It involves understanding how political decisions are made in international contexts and the ideas, norms, and interests that shape those decisions.
There are two broad schools of international relations (IR) theory. Realism and liberalism. Realism argues that the world is fundamentally anarchic and that state actors do not project a unified set of interests in the global arena. The world operates as a series of power struggles between great powers. This means that conflict is the norm in international affairs, and states use military, economic, or diplomatic power to coerce other states.
The alternative to realism is liberalism, which is more of a mixture between realism and institutionalism. It shares the assumptions that realism has—that states are rational and self-interested, that they do not know what other state actors will do, and that cooperation is rare—but argues that international institutions can overcome the anarchic tendencies of the global environment toward conflict by creating norms and rules that encourage mutually beneficial interaction. One variant of this is called institutionalism, which emphasizes the role of multinational corporations, NGOs, and media outlets in shaping international policy. Another is called neoliberalism, which advocates for a more open and democratic international order.