Martingale is where you have one position open, you open a position on the same instrument in the opposite way that is larger than the original.
E.g. If you open 2 lot BUY on EURUSD. Then you open a 4 lot SELL on EURUSD.
This is Martingale which is not allowed.
Hedging #
Where hedging is up to or the same size as the original position.
If you open a 2 lot BUY on EURUSD, then up to 2 lot SELL on EURUSD, this is entirely allowed, hedging is a great way for traders to manage risk.