Bid/Ask

All forex quotes are quoted with two prices: the bid and ask. For the most part, the bid is lower than the ask price.
bid is the price at which your broker is willing to buy the base currency in exchange for the quote currency

ask is the price at which your broker will sell the base currency in exchange for the quote currency.

The difference between the bid and the ask price is popularly known as the spread.

EUR/USD

If bid price is 1.34568 and the ask price is 1.34588.

If you want to sell EUR, you click "Sell" and you will sell euros at 1.34568. If you want to buy EUR, you click "Buy" and you will buy euros at 1.34588.