There are five main categories of troop type, each of which is further divided into sub-categories. For example, particularly large infantry fall into the monstrous infantry sub-category of infantry. In such cases, when the rules refer to infantry models or units, monstrous infantry must also follow those rules unless an exception is stated for monstrous infantry.

A model's troop type also determines the minimum number of such models a rank must contain to claim a Rank Bonus, the maximum Rank Bonus a unit of such models is able to claim, and the Unit Strength of such a model, as shown in the sections that follow.

In most cases it will be fairly obvious which main category of troop type a model falls into. Sub-categories are more complex and exist to help better understand the exact role of a unit in battle and to better reflect this in games through the use of different rules.