Lot is a measure of order volume.
1 lot is equal to 100 000 of base currency.
Please, check how it looks in the Metatrader:
Here the volume size is 1.00, it means that you will trade this order with 1 lot.
Please, kindly be informed that for all account types except Cent account the standard lot size is used.
Kind reminder: 1 lot on a “Cent” account = 0.01 standard lot.