A breakout happens when price moves decisively above a resistance level or below a support level, showing that one side (buyers or sellers) has taken control. A retest occurs when price comes back to test that same broken level—old resistance turns into new support in an upside breakout, or old support turns into new resistance in a downside breakout. This retest is important because it confirms the strength and validity of the breakout; if price holds the level and resumes in the breakout direction, it signals trend continuation and often provides a low-risk entry opportunity for traders.