Lot - the smallest lot in the Forex market with which a trader can enter the foreign exchange market
Each lot consists of 100,000 units of currency. Thus, if you want to buy one lot of a currency pair EUR/USD, you need to have 100,000 units of the main currency, and if you want to sell one lot of this currency pair, you need to have 100,000 units of the opposite, or quoted, currency.
Therefore, a trader who has a long position on a currency pair EUR/USD with the value of one lot, actually buys 100,000 euros, and if it shorts it, it sells the equivalent amount of US dollars.