Since the US dollar is the centerpiece of the market, it is normally considered the 'base' currency for quotes. In the "Majors", this includes USD/JPY, USD/CHF and USD/CAD. For these currencies and many others, quotes are expressed as a unit of $1 USD per the second currency quoted in the pair. For example, a quote of USD/JPY 123.50 means that one U.S. dollar is equal to 123.50 Japanese yen.

When the U.S. dollar is the base unit and a currency quote goes up, it means the dollar has appreciated in value and the other currency has weakened. If the USD/JPY quote listed above were to increase to 124.01, that would mean that the dollar is stronger because it will now buy more yen than before.

Some exceptions to this rule are the British pound (GBP), the Australian dollar (AUD) and the Euro (EUR). In these cases, you might see a quote such as GBP/USD 1.4366, which means that one British pound equals 1.4366 U.S. dollars. In these three currency pairs, where the U.S. dollar is not the base rate, a rising quote means a weakening dollar, as it now takes more U.S. dollars to equal one pound, euro or Australian dollar.

So if a currency quote goes higher, that increases the value of the base currency. A lower quote means the base currency is weakening. Currency pairs that do not involve the U.S. dollar are called cross currencies, but the premise is the same. For example, a quote of EUR/JPY 127.95 signifies that one Euro is equal to 127.95 Japanese yen.