A candlestick chart indicates the ranges of prices of stocks, bonds, or other forms of securities. In the candlestick chart below, data for each month (J for January, F for February, etc.) is summarized. The vertical axis is measured in dollars, and represents the value of a certain stock.
The thick bar in the middle of each month’s price data shows the range of prices between the opening and closing prices for that month. The thin line segments (called wicks) extending above and below the thick bar are used to identify the highest and lowest prices achieved by the stock during that month.
When the thick bar is shaded black, it means the stock price had a net loss for the month (in other words, the closing price is lower than the opening price). When the thick bar is white, the closing price is higher than the opening price for that month.
Reference for image: http://www.itechtalk.com/thread841.html