Dual-axis (or Combination) charts combine Measures in the same view. This can either be to compare different Measures, or to combine the same Measures to create different aesthetic results. This can be achieved via the Show Me panel in some instances, and manually for other purposes.
The first video is courtesy of DataChampions:
Andy Kriebel supplied an alternative way of presenting data which isn’t a dual-axis as such, but is a way of appearing to combine two Mark types in the same chart (only it isn’t the same chart…..):
Ryan Sleeper‘s post is typically comprehensive and easy to follow:
Tableau Online Help also gives a simple overview of this chart type:
The Information Lab always post good walkthroughs, and this one is no exception:
A really valuable article was posted by Data Revelations – exploring the dangers of fixing the y-axis to create misleading results:
Interworks show how to combine maps with other Mark types:
Chris Love at The Information Lab shows a few examples of the sort of variety you can create with dual-axis charts:
This is an extremely common chart type, and you will stumble across them pretty much every day. Many examples tend to be aesthetically driven, so example from the Bump chart post apply.