Charts are used to simplify the trading data in a security.They are made up of price bars which show the open, high, low and closing price for the security during a time period (usually a day, but potentially anything from a minute to a month).The closing price is the most important, which is why it’s normally used to draw price charts (those which show just one line).Most TA indicators work in a similar way to the price bar - they are a mathematical manipulation of the OHLC price data, together with volume.