Microsoft Office Excel 2016: Part 2 (Intermediate) - A dual-axis chart is simply a chart that displays two sets of information on the same chart. The main advantage to dual-axis charts is the ability to not only display two different sets of data simultaneously, but also to format the different sets of data independently of each other. (Dual-Axis Charts, Forecasting, Trendiness, Trendline Types, The Format Trendline Task Pane)