EUR-USD represents short form of euro and U.S dollar currency pair. It shows amount of U.S. dollars in one euro. Here EUR is base currency and USD is quote currency.  The price of EUR/USD pair is read as 1 euro per x U.S. dollars. For example if the price of pair is 1.50 in international market, it shows there are 1.5 U.S. dollars in 1 euro.

Increase and decrease in price of euro and U.S dollar and other currencies impacts on EUR/USD.

Similarly a price chart for a stock, a price indicated on a price chart for a currency pair represents the exchange rate of both currencies. The price that is indicated on price chart is quote currency price corresponds to the base currency. For example, EUR/USD price is at 1.50, as the price rises to 1.70, its mean euro currency has been strong and the U.S. dollar has been weak. At this time, there are 1.70 U.S. dollars in one euro.

1 euro = 1.24 U.S. dollars

Increase and decrease in rates of U.S dollar and euro with respect to each other and other currencies have impact on EURO/USD. So difference of interest rates of federal reserve (Fed) and the bank of Canada (BoC) will have impact the rates of these currencies when compared to each other.