Combination charts essentially bring several chart types together and can demonstrate a direct comparison between different data using the same Y axis or two separate axes. All data groups need to share the same X axis regardless. Combo charts are useful for comparing two different metrics side-by-side.
Combo chart allows for one X Axis Field and any number of Y Axis Fields.
Please note that the Y Axis Fields need to contain numeric fields and remember to select an Expression,Series Type and Axis Position for the Y Axis Fields by clicking on the field first and then choosing from the drop down. Available Series Types include Area, Column, Line and Scatter.