Complete hedging refers to traders placing orders for the same trading instrument and the same lot size, but in opposite directions. This does not occupy any margin. While incomplete hedging does not have the same lot size, it still requires partial margin.
Example: You open a buy order for 1 lot of gold and at the same time open a sell order for 1 lot of gold. You will notice that "Trades" within the MT4/5 Terminal will not show any used margin.

