Stock charts are what traders use as part of their technical analysis of a share. The charts simply display where the stock has been, in terms of price, over a time frame (which you can set). Each bar on the chart usually represents a day, however you can change the time frame of the bars with charting software.
When viewing a chart, traders normally chose between two ways to view the chart, they use either use OHLC bars (open, high, low, close) or candlestick bars.
Stock Chart Example 1
Apple | May 2007 - August 2007 | OHLC chart
(screen shot Telechart)
Stock Chart Example 2
Apple | May 2007 - August 2007 | Candlestick chart

(screen shot Telechart)
Stock Chart Example 3
Apple | May 2007 - August 2007 | OHLC chart close-up
If you take a closer look at the OHLC chart, the day in focus in red. This is because the close price finished lower than the open price.
(screen shot Telechart)
Stock Chart Example 4
Apple | May 2007 - August 2007 | Candlestick chart close up
As with the OHLC graph, the day in focus on the candlestick graph is also red. This is also because the close price finished lower than the open price. The candlestick graph just provides a different visual way of looking at a chart. Choosing between a OHLC chart or a candlestick chart is purely a matter of visual preference.

(screen shot Telechart)
Stock charts are fascinating once you learn the many different types of trading patterns that appear and know the indicators that pretty much tell you when to buy! If you think the charts look complicated you are mistaken, it only takes a little time and practice to understand what they mean.
If your serious about trading stocks and want some 'hands on' experience using charts, I recommend taking a 30 day free trial with Telechart as they offer the best stock charting service bar none.