The basic reason people using retracement tools are any stock before further continuing in actual trend it corrects or recovers little and then continues further. Fibonacci retracement is useful in finding this particular stock behavior.
Fibonacci numbers were named after Leonardo of Pisa, also known as Fibonacci, even though they had already been described earlier in India. The best-known Fibonacci numbers are a simple series of numbers that form a sequence. After two starting values, zero and one, each number is the sum of the two preceding numbers.
The Fibonacci sequence of numbers is as follows: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, etc. Each term in this sequence is simply the sum of the two preceding terms and sequence continues infinitely. One of the remarkable characteristics of this numerical sequence is that each number is approximately 1.618 times greater than the preceding number.
The key Fibonacci ratio of 61.8% - also referred to as "the golden ratio" or "the golden mean" - is found by dividing one number in the series by the number that follows it. For example: 8/13 = 0.6153, and 55/89 = 0.6179.
The 38.2% ratio is found by dividing one number in the series by the number that is found two places to the right. For example: 55/144 = 0.3819.
The 23.6% ratio is found by dividing one number in the series by the number that is three places to the right. For example: 8/34 = 0.2352.
Fibonacci retracement is created by taking two extreme points on a chart and dividing the vertical distance by the key Fibonacci ratios. 0.0% is considered to be the start of the retracement, while 100.0% is a complete reversal to the original part of the move. Once these levels are identified, horizontal lines are drawn and used to identify possible support and resistance levels. The first thing you should know about the Fibonacci tool is that it works best when the market is trending.
The idea is to go long (or buy) on a retracement at a Fibonacci support level when the market is trending up, and to go short (or sell) on a retracement at a Fibonacci resistance level when the market is trending down. In order to find these retracement levels, you have to find the recent significant Swing Highs and Swings Lows. Then, for downtrends, click on the Swing High and drag the cursor to the most recent Swing Low. For uptrend, do the opposite. Click on the Swing Low and drag the cursor to the most recent Swing High.