What is margin?
Margin can be thought of as a good faith deposit required to maintain open positions. This is not a fee or a transaction cost, it is simply a portion of your account equity set aside and allocated as a margin deposit. Margin requirements (per 1k lot for FX and 1 Contract for CFDs) are determined by taking a percentage of the notional trade size plus a small cushion. A cushion is added to help alleviate daily/weekly fluctuations. See FXCM's Margin Requirements.
CFD Margin Requirements (Includes Indices, Commodities, Cryptocurrencies and Treasury Instruments)
Up-to-date margin requirements are displayed in the "Simplified Dealing Rates" window of the Trading Platform by instrument.
You can read more about margin and how it works at https://www.fxcm.com/za/insights/what-is-margin/. Please be advised that trading on margin carries a significant risk of loss and is not suitable for all investors.
Trading on margin can both positively and negatively affect your trading experience as both profits and losses can be dramatically amplified.