The indicator plots the open prices of the bars as a line.
The line color, width and style changed randomly every N=5 ticks. The width, color and style of a line can be defined using the preprocessor directives or using the PlotIndexSetInteger() function. The dynamic change of the line properties allows to create the "live" indicators that vary depending on the current state. Only one data buffer is needed for the DRAW_LINE style.
See also: The Drawing Styles in MQL5.