A chart is the visual representation of an index or a stock's price pattern over a period of time. Price is recorded on the vertical axis and time is recorded on the horizontal. A chart is the basic component of technical analysis. There are many different types of charts that capture various pieces of relevant data and display it in a logical format. The most important function of a chart is to study the historical movement of a market or an individual stock and use the information to try and determine future action. Charts can also be a valuable tool in identifying various stages of a trend.