Condition expression must return a Boolean value, and is used to determine when the waypoint execution is terminated.
On Activation expression defines action that is peformed after the waypoint is terminated.
The variable this is set during the evaluation of the condition to the primary waypoint termination condition (i.e. if the waypoint is of the type "Move" the variable this would contain the name of the lead unit, once the waypoint in reached).
The array thisList is set to list of all units in the group that given waypoint is assigned to.