Troop cards allow you to order a specific unit type (Example: light, medium) to move and/or battle. Unless the card states otherwise, you may freely choose Foot or Mounted units... So “Order Light” means you can issue your allotment of orders to any combination of light Foot units or light Mounted units. Ordered units may be in any section of the battlefield. The number of units you may order is equal to your side’s Command, i.e. the maximum number of cards you may hold in your hand on that turn. (See “Command” under section 07. ORDER UNITS AND LEADERS.)
Note: If you have units of a troop class anywhere on the battlefield, you may not use a troop card to order the 1 unit of your choice option.