What does the "Protect" modifier do?
The "Protect" modifier is only available for Market orders and it's for users who want: (1) High certainty of execution, and (2) Limited risk of bad execution price. A protected Market order will be sent as a Limit order with a price equal to True Price +/- Protection Depth percentage (addition for a buy order, subtraction for a sell order). Protection Depth is set to 0.1% but is configurable in the Trading widget settings. The limit price will be visible in the order ticket and will update real-time.
Example: The market in BTC-USD is 9,999 at 10,001 and True Price is 10,000. With a 1% protection depth, a buy order will be sent with a limit price of 10,100, while a sell order will be sent with a limit price of 9.900. The exchanges will deliver you the best available price from the order book that is at or inside of the limit price. So you get the same execution as you would with a market order, but without the risk of trading too far away.