There are 4 types of cards - units, specials, artefacts and stratagems.
In each type there are different tags. For example,
Units have 'human', or 'elf' or 'beast'
Specials sometimes dont have a tag, others have a faction-specific: NR has 'warfare', SK has 'raid', ST has 'nature',
but there are also certain tags, like 'Alchemy' or 'Tactic', that are not faction exclusive but are more associated with a certain faction (SK and NG respectively, for these last i mentioned).