Warhammer is a miniatures-based fantasy/sci-fi war game. People enjoy it because instead of strategizing you can win by investing more money in the game.
Unlike Magic: The Gathering, where you have to buy multitudes of sealed booster packs before getting the cards you want, you instead spend hundreds of dollars on tiny plastic or metal figurines and paint them. The past part is, at the end of the day, instead of worthless little pieces of cardstock, you have worthless little figurines.
The game can look very realistic and exciting on the table, with dark elf priestesses with huge headdresses that have flaming swords, chainsaws, but no pants. The game features realistic warfare as well, with tanks and artillery pieces that can fire distances of almost a football field.
-S