In Warhammer, the opposing factions - the armies - are represented by models, assembled and painted by you.
Your tabletop becomes part of the Warhammer world, be it the steaming jungles of Lustria, the wind-swept plain of Kislev or the forbidding forests of the Empire.
The aim of the game is to outfight your opponent, which requires a mixture of both skill and luck. You'll soon learn how to arm and design your army effectively, and how to exploit the terrain to your best advantage.
You'll probably want to expand your basic force as you play more games. This is easy as there are lots of models available for all the armies and new miniatures will be coming out all the time. With these you can expand your army, equip your heroes with different weapons and armour and hire mercenaries to join your force.