The price of any stock can be tracked using a price vs time chart. Here the high and low points of the option can be easily seen in any given amount of time.
Fibonacci Retracements use the high and low points of each option to trace horizontal lines over top of the chart. 100% and 0% lines are traced at the high and the low points, respectively. Three additional lines are added in between at 61.8%, 50% and 38.2%. These percentages have been determined mathematically and are the same for all Fibonacci Retracements.