What Is International Economics?

International economics is a field of study that assesses the implications of international trade, international investment, and international borrowing and lending. There are two broad subfields within the discipline: international trade and international finance.
International trade is a field in economics that applies microeconomic models to help understand the international economy. Its content includes basic supply-and-demand analysis of international markets; firm and consumer behavior; perfectly competitive, oligopolistic, and monopolistic market structures; and the effects of market distortions.

Source:
International Economics: Theory and Policy
Available on http://www.saylor.org/site/textbooks/International%20Economics%20-%20Theory%20and%20Policy.pdf