In the Forex market, the margin is a minimal sum of money that an investor needs to open a position. Thus, a broker allows using leverage in your trading. Forex broker sets the requirements of the margin for clients itself.
Option margin is the capital or securities which should be deposited into the trader’s account before writing (selling) an option. Margin is collateral (an asset that a lender accepts as security for a loan) to secure a position. The margin requirement for options is quite complex. The minimum margin requirements are set by FINRA and options exchanges. Margin requirements of brokers may differ because they can add additional sum to the minimum requirements of regulators.