Chart Types Used in Technical Analysis
A main method technical analysts use to forecast security prices is recognizing patterns and trends of security prices, and the easiest way to spot patterns and trends is with charts. Using charts is so prevalent that technical analysts are often called chartists. Originally, charts were drawn by hand, but nowadays, they are drawn by computer.
Charts are graphical displays of security prices and possibly trading volume over time. Besides allowing the technical analyst to easily spot patterns and trends, the main benefit of charts is the concise presentation of price and volume information over a duration, which fundamentalists can use to study how the market has reacted to specific events. Market volatility can also be easily gleaned from charts. Charts help technical analysts decide on entrance and exit points and at what prices to place stops to reduce risk.
The primary types of charts used by technical analysts include line charts, bar charts, candlestick charts, and point-and-figure charts. These charts can be displayed using either an arithmetic or a logarithmic scale. The choice of chart type and scale depends on the specific information that the technical analyst deems most important and which format best represents that information.
Chart Scales: Arithmetic and Logarithmic
Most charts display price intervals on the vertical axis and time intervals on the horizontal axis. A chart based on the arithmetic scale (aka linear scale) shows the same distance between equal price differences. So, a $10 stock that increased by $10 would be plotted up by the same amount as a $100 stock that increased by $10, even though the $10 stock doubled in price while the $100 stock only increased 10%.

The logarithmic scale (aka semi-logarithmic scale) uses percentages as the primary unit rather than absolute differences. On a logarithmic scale, a $10 stock increasing by $10 would plot higher than a $100 stock rising by $10. Hence, a chart based on a logarithmic scale presents price change information more accurately than a chart based on an arithmetic scale. A chart based on the logarithmic scale can also cover a wider range of prices than a chart of the same size based on the arithmetic scale. However, for narrow price ranges, the 2 scales do not differ much.

Line Charts
Line charts are the simplest form of charts depicting price changes over time. Usually, only the closing price is graphed, depicted by a single point. The series of these points constitutes a line — hence, the name. However, intraday price changes can also be plotted, either by plotting each trade, or by selecting the last price of a given interval, such as an hour or 15 minutes. Because line graphs are simple, it is easier to compare the prices of multiple securities or indexes on the same graph.
The line chart also shows trends best, which is simply the slope of the line.

Bar Charts
A basic tool of technical analysis is the bar chart, where the open, close, high, and low prices of stocks or other financial instruments are embedded in bars which are plotted as a series of prices over a specific time period. Bar charts allows traders to see patterns more easily. In other words, each bar is actually just a set of 4 prices for a given day, or some other time period, connected by a bar in a specific way — called a price bar.
A price bar shows the opening price of the financial instrument, which is the price at the beginning of the time period, as a left horizontal line, and the closing price, which is the last price for the period, as a right horizontal line. These horizontal lines are called tick marks. The high price is depicted by the top of the bar, the low price by the bottom.

Candlestick Charts
Another type of chart used in technical analysis is the candlestick chart, so called because the main component of the chart representing prices looks like a candlestick, with a thick body, called the real body, and usually a line extending above and below it, called the upper shadow and lower shadow, respectively. The top of the upper shadow represents the high price, while the bottom of the lower shadow represents the low price. Patterns are formed both by the real body and the shadows. Candlestick patterns are most useful over short periods of time, and mostly have significance at the top of an uptrend or the bottom of a downtrend, when the patterns most often signify a reversal of the trend.
While the candlestick chart shows similar information as the bar chart, certain patterns are more apparent in the candlestick chart. The candlestick chart emphasizes opening and closing prices, represented by the top and bottom of the real body. Whether the top represents the opening or closing price depends on the color of the real body — often it will be white or green if the top represents the close; red or black or some other dark color, indicates that the top was the opening price. The length of the real body shows the difference between the opening and closing prices. Obviously, white or green real bodies indicate bullishness, while red or black real bodies indicate bearishness, and their pattern is easily observable in a candlestick chart.
Point-and-Figure Charts
Point-and-figure charts list only significant price information as columns of X's and O's without regard to time, so that trends, resistance and support levels are more apparent. Although time is depicted on the horizontal axis, the units of time are determined by when the trend changes.
Point-and-figure charts can be constructed in several ways, but all are based on box size, the minimum price differential necessary before a price is recorded as an X or an O. Columns of X's show an uptrend, and O's show a downtrend. Generally, closing price differentials are used. There is no high, low, opening, or closing prices recorded since only the change in price exceeding the box size is recorded as an X if the price differential is up or as an O if it is down. Each consecutive X is recorded in the same column above the previous X until the price reverses by more than the box size, then a new column is started by recording an O in a box below and to the right of the highest X in the previous column. O's are added downward with each price decrease exceeding the box size until the downtrend reverses to an uptrend, starting a new column where the 1st X is placed in the box above and to the right of the last O in the previous column.
For example, if the box size is 1 point, the rise of a stock from 10 to 11 is recorded as an X because the price rose by at least 1 dollar. The stock rising only $.50 would not be recorded since the price increment was not at least the box size of 1 dollar. If the price increased by at least 1 dollar the next day, another X would be recorded above the previous one in the same column. If the next day, the price declined by $.25, nothing would be recorded since the change is less than the box size. If, on the next day, the price declined by more than 1 dollar, a new column of O's would be started with the 1st O recorded 1 box below the top X of the adjacent column. Each time the price declined by more than the box size, another O would be placed below the last O of the column. When the stock rises by more than the box size, a new column of X's would be started, with the 1st X placed 1 box above the bottom O of the adjacent column. Note that, except for the first and last columns, each X column is flanked by O columns, and vice versa.
The construction of point-and-figure charts simplifies the drawing of trend lines, and support and resistance levels, so point-and-figure charts are ideal for detecting trends, and determining support and resistance levels.

This seems to be the most common type of point-and-figure chart, but keep in mind there are several variations differing significantly from the above description.