High Elves: Bonus experience and reduced recruitment and upkeep costs for Archers, Spearmen, Lothern Sea Guard and Bolt Thrower units Dark Elves: Bonus experience and reduced recruitment and upkeep costs for Dreadspears, Darkshards, Shades and Reaper Bolt Thrower units
Timber is one of the resources available in the campaign mode. Extracting it requires building a specific building chain.
Wood is a flexible resource, used in anything from buildings to hand weapons. Just be careful which trees you take it from, as some won't take kindly to being felled.