The major differences between these two strategies are in the type of good that each strategy tries to produce and the sorts of international economic policies they promote.
In the import substitution strategy, the country tries to produce the things that it now must import. For example, a less-developed country today might start to try to produce cars so that it does not need to import them. Such a country might also resort to the creation of trade barriers to block imports.
In the export-led strategy, the country tries to produce things that it can sell to other countries. Countries like Japan and China have pursued this strategy. They have produced things like electronics to sell to other countries rather than for domestic consumption. Such countries will try to promote free trade so that they can sell their products in foreign markets.