Take world generation for example. The first thing a player must do upon starting the game is have a random world generated. This world is formed with surprising realism. Mountain ranges form in realistic lines, rivers will flow across the land, carving out fertile valleys, and rain shadows will form deserts on the far sides of mountain ranges.

Then an extensive history for this world will be generated, with civilisations rising and falling, titans raiding towns, wars being waged, heroes appearing, etc. This will all be reflected in the factions that visit your fortress, and in the areas your hero can explore.

Physics also play a prominent role in the game's functionality. In a seemingly simple action, such as a dwarf swinging a hammer at a goblin, so many factors come into play. The game will consider the force of the dwarf's swing, the quality and material of the dwarf's hammer (a silver one would be heavier than a copper one, and therefore more effective), the thickness and quality of any armour the goblin may be wearing (which is also dependent on the specific body part struck), how many layers of armour and clothing there may be, the thickness of the goblin's skin, muscles, and bones, and more.

Through all of this, the game subverts typical damage-tracking in the form of hit points, and instead uses a broader, somewhat more vague system in which body parts may be bruised, cut, broken, mangled to various degrees, or lopped off entirely. On top of all that, the game also considers any cut arteries, severed nerves and even the character's personality.

Discussing all the game's mechanics requires an entire book (and indeed there are books and even theses on them), but, thanks to the interplay between these systems, one of the biggest draws to Dwarf Fortress is that it's a great storytelling game.