Globalisation is basically interconnecting the world, in this case with respect to national economies via trade. Barriers of trade is self explanatory, ie anything that restricts the flow of trade；tariffs, cultural diff, legal regulations.
Trade barriers is tariffs, subsidies, quotas, local content rules and export incentives. Globalisation is based on the theories of absolute and comparative advantage i.e. countries should produce stuff that they are good at producing and trade it with others for greater productivity globally or higher GWP.