Mathematical levels (23.6%, 38.2%, 50%, 61.8%, 78.6%) where corrections often end and trends resume.
Example
Bitcoin rises from €50,000 to €60,000, then corrects. Traders draw the Fibonacci retracement over that move: the 61.8% level sits around €53,800. Price often slows right there and the uptrend resumes. The key levels are 38.2%, 50% and 61.8%. Fibonacci is not magic — it works because many participants watch the same levels and trade around them.