Fibonacci Retracements are displayed by first drawing a trendline between two extreme points, i.e. a trough and opposing peak. A series of horizontal lines are drawn intersecting the trendline at the Fibonacci levels.
After a significant price move in either up or down direction, prices will often give back a significant portion (if not all) of the original move. As prices retrace, look for support and resistance levels often occurring at or near the Fibonacci Retracement levels.