A deliberate downward adjustment to the value of a country’s currency, relative to another currency, group of currencies or standard. Devaluation is a monetary policy tool of countries that have a fixed exchange rate or semi-fixed exchange rate. It is often confused with depreciation, and is in contrast to revaluation.
Devaluating a currency is decided by the government issuing the currency, and unlike depreciation, is not the result of non-governmental activities. One reason a country may devaluate its currency is to combat trade imbalances. Devaluation causes a country’s exports to become less expensive, making them more competitive on the global market. This in turn means that imports are more expensive, making domestic consumers less likely to purchase them.
While devaluating a currency can seem like an attractive option, it can have negative consequences. By making imports more expensive, it protects domestic industries who may then become less efficient without the pressure of competition. Higher exports relative to imports can also increase aggregate demand, which can lead to inflation.
Best example of currency devaluation is of recent China’s Yuan devaluation.
Source: investopedia