When an economist says that a currency has become stronger he or she means that?

A strong currency occurs when the value of a country's currency has risen to a level against another currency that is near historically high exchange rates. This means that a currency is worth more relative to other currencies. Because most currencies are floating, their values vary according to market trends. When one unit of currency trades for more units of another, it is said to be a strong currency. The advantage of this is, travelers are able to go abroad while spending less of their money, also it makes exports more expensive in other countries.

It can be exchanged for more of a foreign currency