Path is represented with the  icon.

Path is a property available for both Line and Polygon. 

Since 2018.1, when using the Line Mark type, clicking on the Path button opens a menu where you can select the Line type: Linear, Step, or Jump. Here's an example of a Step Line:

This property allows you to choose the order to connect the Marks. You can use either a Dimension or a Measure.

It's quite rare to use this property. Usually, you only use it if, in your data, there is a special  order to connect the Marks to create a specific visualization. 

The next and last property only exists for Pie.