Core terms
Trailing stop
A stop that moves in the trade's favour behind price, by a set number of cents, a multiple of R or the low of the last completed bar, and does not move back. It exits with a stop order, so it pays slippage.
A trailing exit keeps more of long runs than a fixed target and gives back at least the trail distance on every trade that reaches it. Brokers offer trailing stop orders that follow price by a set dollar amount or percentage (FINRA, Types of orders); many scalpers trail by hand or by hotkey using bar lows or R steps instead.
A triggered stop order becomes a market order, so in a fast drop or around a halt the fill can be several cents below the trail. A trail inside ordinary 1-minute noise exits on that noise; a wider one gives back more. On the same entries, MFE gives the best case for a trailing rule, but the actual exit depends on the price path after the high.
What traders should verify
Write the trail rule (distance, step and when it starts) before entry, and log both the trail price and the actual fill so slippage on trailing exits shows up in R.
Do not conflate
Trailing stop orders are broker features, and their handling of sessions, halts and trigger prices differs between brokers; bar-low and R-step trails are trader usage with no official definition. A trail does not cap the loss at its price: gaps, halts and fast markets can fill it well below.
Primary source
Primary sourceFINRA, Types of orders