This property is designed to let you ‘tease out’ a 3rd dimension from a scatter-plot to show the effect of a category variable.

ch.Set'Head' 'Yield vs Farm, teased by Year'
ch.Set('style' 'boxed')('xs' 'grid')('ma' 'lozenge')('tease' 6)
ch.Scatter yield vs farm by year

This effectively adds a 3rd dimension to the normal 2-D scatter plot by pulling the categories apart in the X-direction. The ‘tease’ value is the distance in points to separate each category; the separated categories are teased symmetrically about each x-value. If you have a large number of categories, you will need to use a low value here to prevent adjacent groups merging into one another.

See also ...
ch.Boxplot – box and whisker charts
CategoriseBy – category variable