the value of the dollar in terms of other currencies
Businesses are affected by it because:
they buy rawmaterials from abroad
they sell their goods overseas
Companies are concerned about exchange rates as flunctuations can make a difference between trading at a loss or at any profit.
Strong dollar — need more currencies to exchange for one dollar. Our goods are expensive overseas, lower demand for our exports.
Weak dollar — need fewer currencies to exchange for one dollar. Our goods are attractive to foreigners as they seem cheaper, our imports are more expensive.