Below is a diagram showing the broad categories of U.S. international taxation segregated into "inbound" topics, "outbound" topics, and overlapping topics.As indicated in the diagram, "inbound" generally means foreign persons (e.g., foreign corporations, nonresident aliens, etc.) with U.S. income, and "outbound" generally means U.S. persons (e.g., domestic corporations, U.S. citizens and residents, etc.) with foreign income. Click on image to enlarge.
For related blog post see inbound-outbound.