On the Forex
1 lot is a standard trade volume. It is similar to a liter or a kilometer for the liquids and distances. You specify the volume for each trade when you set the parameters of your order. The minimum trade volume for market entrance is 0,01 lot (0,1 for the Micro accounts).
1 lot is 100 000 of the base currency working on the market. For instance, you have $500 in your account. It is 0,005 lot (500 / 100 000 = 0,005), but you also have leverage 1:100. Thanks to leverage, you can enter the market with a total trade volume of 0,005 * 100 = 0,5 lot. This is 1 order with the volume 0,5 lot, or 5 orders with the volume 0,1 lot, or 50 ordered with the volume 0,01 lot, or 2 orders with the volume 0,2 lot + 1 order with the volume 0,1 and so on.
When trading stocks and CFD
1 lot is a standard trade volume. It is similar to a liter or a km for the liquids and distances. In 1 lot there can be a various number of asset/stock units depending on the instrument. The minimum trade volume for market entrance is 0,01 lot.
In MetaTrader4 you can find information on how many units of stocks/assets amount to 1 lot of a chosen instrument. To do this, right-click the name of an instrument in the window “Market review” and choose “Specifications”. The values are shown in the column “Contract size”.