Hi there,
basically a trading bloc is where a number of countries agree to band together in a trading agreement excluding other countries. Examples of a trading bloc are the European Union and the North America Free Trade agreement. In these trading agreements countries must join by adopting certain requirments set out by the agreement, such strict legislative changes on trading practices, and if they don't join then exports to countries within the trading bloc will be difficult or near impossible, because the importing country will have obligations under international trade law to only import(and export) to countires within the trading bloc.
Essentially its a protectionist measure, designed to only benefit countires within the trading bloc, and is in contrast to free trade agreements where protectionist measures are abolished. It also hinders global trade flows, an example of this would the difficulty in exporting Australian beef or wool to countries within the EU. This is because countries that would have previously imported such Australian products before joining the EU, are now no longer able to do so, as they are obligated to import such products from EU nations.
Hope that helps
