Line of sight determines what a model can 'see'. Many situations call for you to determine whether or not a model has line of sight. A model normally needs line of sight whenever it wishes to attack an enemy, whether with sword, spell or bow.
Line of sight literally represents your warriors' view of the enemy – they must be able to see their foe through, under or over the battlefield terrain, and other models (friendly or enemy).
For one model to have line of sight to another, you must be able to trace an unblocked line from the front arc of its base to the base of the target. However, models with a higher Line of Sight value can see and be seen behind models or terrain with a lower Line of Sight value.
For more information about the different Line of Sight values, see thechapter for models, and chapter for terrain.
Example: A model with Line of Sight value 2 can see and be seen behind a model with Line of Sight value 1, but cannot see or be seen behind a model with Line of Sight Value 3.