Iron is a type of non-organic material, derived by forging from iron ore, a mineral resource.
Items made from iron (including steel items) are derived from this material.
Iron cannot be mined in the game, or traded in the form of iron ore. The only manner in which items containing iron, be they tools, containers, weapons or even armour, can be acquired, is by trading at various settlements. Some cultures will have more readily available iron or steel items than other cultures, depending on the geography of the region they inhabit.
Real life context
URW Game Encyclopedia description
The official URW in-game encyclopedia (accessed by the key) describes iron thusly:
Armour which forms a rigid continuous covering and is made of iron. Iron armours are relatively rare. Its use is generally restricted helms, and small plates for spot protection. Iron armours offer good to excellent defense against all strikes.
The official URW in-game encyclopedia (accessed by thekey) describes mail (armour) thusly:
Interlocking metal rings, usually half an inch or less in diameter. Mail may be butted, coiled or rivetted, these considerations are reflected by armour quality. While mail is a superb defence against edged weapons, and reasonable against the point, it does little to reduce force of a blow, and may be driven into its wearer's flesh. Because of this, leather or wool garments are usually worn underneath.
The official URW in-game encyclopedia (accessed by thekey) describes lamellar armour thusly:
Lamellar is eastern armour type used by Njerpezit. Lamellar armours are made of square or rectangular iron plates tightly fastened to each other with leather straps passed through openings along the edges of the plates. Lamellar technique is used mainly to create cuirass and hauberk type armors, but it's also suitable for some spot protection pieces like shin guards and forearm guards. Lamellar armour offers better protection than mail, especially in case of blunt attacks.
Iron items in the game.
Knives with iron or steel blades and a wooden or antler grip.
Axes with iron or steel blades and wooden hafts.
Spears with iron or steel blades and wooden shafts.
All of the available swords are made from iron or steel.
Iron and steel armour
Includes mail armour, made from steel rings, and lamellar armour, made of interconnected small iron plates (lamels).
In-game encyclopedia entry on iron armour
In-game encyclopedia entry on mail armour
In-game encyclopedia entry on lamellar armour
Shields are wooden, but include iron bosses at the centre of the outer side.
An iron or steel arrowhead is used on the broadhead arrow, giving it a slicing capability that inflicts bleeding wounds.