1 There are two types of glial cells in the nervous system: the large-bodied macroglia and the smaller microglia. 2  There are two classes of macroglia in the central nervous system: astrocytes and oligodendrocytes.
Exports directly contribute and imports directly reduce their nation's balance of trade (i.e. net exports). A trade surplus is positive net balance of trade, and a trade deficit is a negative net balance of trade.
Trade, in general connotation, means the purchase and sales of commodities. In International Trade, purchase and sale are replaced by imports and exports. Balance of Trade is simply the difference between the value of exports and value of imports. Thus, the Balance of Trade denotes the differences of imports and exports of a merchandise of a country during the course of year. It indicates the value of exports and imports of the country in question.