Leverage or use of non-specified ratio (debt ratio to net assets).

To make it simple, leverage is using the borrowed money when investing.
The higher the leverage the higher the risk level. if you have a good money management strategy you will earn extra money by using leverage. On most of the brokers, you can only trade by choosing fixed leverage. It means if you set your account to X20 leverage all of your trades will be executed with the 20 leverage until you change the settings in your account. But some other brokers are more flexible. At eToro you can open diffrent positions using diffrent leverage.

Using high leverage will increase the risk and you may lose all the money in your account very fast. Although you are increasing the potential to make profit fast, you can also lose money. You can make lots of profit with borrowed money or lose all your money. At the moment more than 76% of the account on eToro losing money. For example, with x20 leverage, a 5% move in price against your prediction will wipe your account. But a 5% move in your favour will make you almost 100% profit.

You also need to take into the account all the fees and charges like; spreads, overnight and over weekend fees etc.