Purchasing Power Parity, or PPP, is the idea that a country's purchasing power is directly related to the exchange rate of their currency. Gross Domestic Product, or GDP, is a broader economic measure to evaluate a country's economic health because it takes into account goods and services produced, personal consumption, an inventory of private investments, government purchases, and the balance of foreign trade.
There are two types of GDP however, nominal GDP, which is the raw data, and real GDP, which takes into account all of the above. A real GDP is considered the best indicator of a country's economic health.