Net export effect (or exchange rate effect) is one of the explanations of a downward aggregate demand curve.
All other things unchanged, a lower price level in an economy reduces the prices of its goods and services relative to foreign-produced goods and services. A lower price level makes that economy’s goods more attractive to foreign buyers, increasing exports. It will also make foreign-produced goods and services less attractive to the economy’s buyers, reducing imports. The result is an increase in net exports. Therefore, the net export effect is the tendency for a change in the price level to affect net exports.