what is exchange rate?

Because currencies are traded in pairs and exchanged one against the other
when traded, the rate at which they are exchanged is called the exchange
rate. The majority of currencies are traded against the US dollar (USD), which
is traded more than any other currency. The four currencies traded most
frequently after the US dollar are the euro (EUR), the Japanese yen (JPY), the
British pound sterling (GBP) and the Swiss franc (CHF). These five currencies
make up the majority of the market and are called the major currencies or
"the Majors". Some sources also include the Australian dollar (AUD) within the
group of major currencies.
The first currency in the exchange pair is referred to as the base currency.
The second currency is the counter currency or guote currency. The counter
or quote currency is thus the numerator in the ratio, and the base currency is
the denominator.
The exchange rate tells a buyer how much of the counter or quote currency
must be paid to obtain one unit of the base currency. The exchange rate also
tells a seller how much is received in the counter or quote currency