Difference between the International Dollar and PPP
They are different stages of the same process. You convert a country's GDP into international dollars USING PPP. 

PPP are rates. They are a relation between prices in different countries. International dollars is a unit of measurement. 

The World Bank says "GDP per capita based on purchasing power parity (PPP). PPP GDP is gross domestic product converted to international dollars using purchasing power parity rates. An international dollar has the same purchasing power over GDP as the U.S. dollar has in the United States"