It shows the motion pattern of two or more indexes on a single chart.
I’ve read that the “auto_detect_pair” parameter should be equal to “false”, at the same time you can specify what exactly indexes to display with the “show_USD” and so on, the default one is to display all. The description of all parameters is in the source code. Look through the code.
One thing more – indexes are united to one point at the beginning of every week, i.e. the base point is changed with the coming of every new one – the close prices of the previous week are used.