What It Means
SL and SL-M are the two stop-loss order variants on Indian exchanges. SL (Stop-Loss Limit) triggers a limit order once your trigger price is hit, giving you price control but no guarantee of a fill. SL-M (Stop-Loss Market) triggers a plain market order instead, guaranteeing execution but not the price you get.
How It Works
An SL order needs two prices: a trigger price and a limit price (usually set a little worse than the trigger to leave room for a fill). Once the market touches the trigger, a limit order goes live at your limit price — but if the price jumps straight past it, the order can sit unfilled. An SL-M order needs only a trigger price; once hit, it converts straight to a market order that fills at whatever price is next available.
Example
A stock at ₹500 gaps down. With an SL order (trigger ₹480, limit ₹478), a straight fall to ₹470 with no trade in the ₹478–480 band leaves your stop-loss unfilled — you're still holding the position. With an SL-M order (trigger ₹480), the same gap fills you out at ₹470 or wherever the market is, guaranteeing your exit at the cost of a worse price.
Warning
SL feels safer because you control the price, but an unfilled SL order in a fast-gapping stock means your position stays open and unprotected exactly when you needed it capped.