International trade is one way to stimulate economic growth. Depending on the economic capabilities of the country in question, imports or exports can be used. A good example is China and the US. China created growth through expansion of manufacturing and exports because it had no opportunity for domestic sales of its manufacturing (not enough money in the population) so it needs to sell wares to countries with money at a low price. Now it’s people have grown in wealth and they have a growing domestic market so they will now focus more on domestic consumption. US has domestic markets and high wealth so it is in their best interest to buy at a lower price - facilitated by low cost manufacturing in China as one example.

This is highly simplified version of course since there is lots of complexity existing within each country/market/commodity - and this all really has to do with markets and not countries at all. However as a general rule you manufacture and sell export when you don't have a domestic market and want to stimulate growth. When you have a mature market and need to maintain lower pricing, you import from lower cost manufacturing centers. There is also a market for imported “l(fā)uxury” goods based on supply/demand which opposes the above but it is very small in comparison and obviously has nothing to do with the countries involved in the trade.