I have decided to cut and paste them here as a reference for myself and others should they be unable to remember what they do. It is also quicker than using the help files in game especially if you are on a newer PC that may not have the updated Windows 7 Help File fix
Optional Rules Dialog
The Optional Rules Dialog is used to view and select the Optional Rules for a new battle. Optional Rules can be set at the beginning of a battle, but not changed once the battle has started. The Optional Rules selected in the Optional Rules Dialog are saved and become the subsequent default for new battles.
Optional Fire Results – when this rule is selected, each fire result is calculated as the average of two normal fire results. This has the effect of reducing the variation in results.
Optional Assault Results – when this rule is selected, each assault result is calculated as the average of two normal assault results. This has the effect of reducing the variation in results.
Helicopter Hovering – when this rule is selected, helicopters can enter the state of Hovering by performing certain actions. In this state, they are more vulnerable to enemy fire. More information on this rule can be found in the Users Manual under Hovering in the section on Movement.
Vehicle Fire Over – when this rule is selected, it is possible for Vehicles to fire over On Ground units of the same side. For more information, see the section on Firing in the Users Manual.
Variable Ending – when this rule is selected, it is possible for a scenario to continue past the specified last turn. For each 10 turns, or fraction of 10 turns, of the original scenario, the duration can be extended up to one additional turn.