Retracement and extension levels from any price swing.
Fibonacci retracement levels (23.6%, 38.2%, 50%, 61.8%, 78.6%) are commonly used to identify potential support and resistance zones after a price swing. The 61.8% level (the "golden ratio") is watched most closely by traders.
Fibonacci levels work best when they confluence with other technical factors: prior support/resistance, moving averages, volume nodes, or round numbers. Alone, they are low-probability. In confluence, they can be high-probability entry points.