Margin VS Leverage

Margin is the actual amount of money that is used by the trader to open a leveraged position.

Leverage is ratio (for example 1:100), which shows the relation between the margin and the actual value of the position.
 
Margin means the money you need to deposit to open a position
Leverage is 1:100 is the amount that your position is inflated

For 1:100 leverage means that you can buy 1 lot usd with 1000 deposit in your account, this 1000 deposited will be the required margin to open this 1 lot postion.