A bracket wraps a trade in its exit rules: the entry, a stop-loss below, and a take-profit above (for a long). When one exit fills, the other cancels, which is the oco-order logic.
Brackets enforce discipline because the risk is defined before you are in and emotional. Most futures and stock platforms support them natively.
Example: buy 1 es contract at 5,000 with a bracket of stop 4,992 (8 points, $400 risk) and target 5,016 (16 points, $800 reward).
Related: oco-order, stop-loss, take-profit, risk-reward-ratio