‘Trigger Price’ is the price at which a buy or sell order has to be triggered. Usually trigger prices are associated with Stop loss.
Stop Loss Trigger Price: Means Suppose you have purchased Reliance at Rs-900, you want to sell at higher price but it is supposed to go down side also may be at 800/- so you will keep a Stop Loss at Rs-880 where prevailing rate in Market is 905. Your order will be executed only if rate touches Rs-880 level. If rate turns back from 880.20 your stock will not be sold.