This function isn't used in first-person games. It can only be edited and used in third-person games.
When an action has this field activated it means that the character will have to walk to the object in order to perform an operation. If the character can not reach the object (e.g. because there is a barrier in between) the action will not be performed.
Besides, when the field is active the distance between the character and the object can be edited. The character will try to stay at that distance before performing the action.
If the field is not activated the character will not move and perform the action from its place (if the other conditions are already true).