Activity evaluates an expression and chooses between one of two paths, depending on if the value is True or False.

By default, paths are labelled True and False, but their names can be changed in the activity properties.

Expression can be seen when hovering over the Flow Decision activity block.

There is a little triangular mark in the upper-right corner of the activity used in scenario. Click on it to make the condition fixed on screen. Click again to make it disappear. To show all conditions in the scenario at once use option Show All Conditions from right-click menu (available on Flow Decision, Flow Switch <Int32> and  Flow Switch <String> activities). To hide them again use Hide All Conditions.

This activity is meant to be used on the flowchart.