An "If/Then" Order is a combination of one main and two additional inactive orders. The main order's purpose is to open the position, while the purpose of the two additional orders is to close it. Once the main order is fulfilled and the position is open, the two inactive orders will become active pending orders.
If you place an Entry Pending Order for a long/short position and you enable Take Profit and Stop Loss orders at the same time, the order is considered "If/Then". The Entry Pending Order will open the position when the price is reached and the other two will remain pending until one of their prices is met and the position will then be closed.