Land types influence one's movement speed, as well as the force of its attack. Most units are considerably less effective against units located in woods or mountains. For instance, cavalry is only effective on plains and losses half of its strength in the woods. The land type taken into consideration is the one onto which an attack or movement is being conducted.

Landscape

Plains
Main land type present in the game.
Units consume 1 AP while moving on this type of land.

Roads
Roads allow rapid transportation for most types of units: 0.5 AP used for passage.

Water
Rivers and seas occupy a large amount of world's surface. Only flying units and ships can move on water.

Woods
Woods provide timber. Meanwhile, they also hide dangers within, like orcs and monsters. Most units need 2 AP to pass through forests.

Mountains
Mountains form natural barriers. Most units consume 3 AP while passing through these cells. Serfs use mountains as a stone source.

Swamps
Movement through swamps consumes 2 AP. You can cultivate mandrake on swamps.
Swamps can be drained with builders; 20 AP needed to complete this goal.

Town / village
Entering a city, no matter what land type lies underneath it, will generally consume 0.5 AP.

Transport
You need 1 AP to enter any kind of transport.