Relative Performance chart compares the rate of price change of two or more tradable instruments. Plot starts with 0% at the very first visible bar and shows percentage change of closing price since that point for every symbol in the list. Relative perfomrance charts are great for comparing dissimimilarly priced issues (for example stocks and indices) since it displays percentage changes, not absolute values. You can easily see which instruments perform better than others and choose best performers for your trading.
You can adjust the list of symbols that are plotted in the Relative Performance chart by clicking with RIGHT mouse button over the chart and choosing "Parameters" item from the context menu. In the Parameters dialog you can enter a comma-separated list of symbols that you want to get the chart for. There is no limit on number of symbols you can enter, but please remember to separate symbols by comma and not using spaces unless symbol itself has them.