Armour is any item in Runescape that provides combat bonuses. There are three types of armour Melee, Ranged and, Magic.
Melee armour is made of metal and provides good protection against ranged attacks. It is weak against magic. Most melee armor requires a player to reach a certain defence level before it can be put on.
All players can use bronze and iron armour as it requires only one defence. Steel provides more protection but requires five defence. Black armour can not be smithed by players. It is only found as a drop. It is considered a symbol of wealth for lower level players it cost more than the stronger mithril armour for this reason most players skip black and upgrade to mithril from steel. Black requires 10 defence. Mithril is great for lower levels, much stronger than steel but requires 20 defence. Adamant is strong armour used by medium level players. It requires 30 defence and may take some time for a player to get there first set of it. Rune armour is considered the best Armour for most melee players. A player getting their first set of rune is good achievement. Most of them have worked on resource gathering skills,mining or woodcuting, or have saved up money from selling drops.
Unlike melee armour, ranged armor requires defence and a ranged level to wield. Ranged armor offers average protection against most attacks, but its speciallty is that it offers protection against magic attacks. Ranged armor is also very cheap; a full set of green dragonhide costs no more than 10k. For new players and starting rangers, there is leather. There is no requirements to wear leather, and it is very cheap. For players with 10 defence, you can replace your leather body with a hardleather body, which offers more protection. Then, there is studded armour. This armor requires 20 ranged and 20 defence to wear. A coif counts as studded armour. Finally, there is green dragonhide, wich requires 40 ranged and 40 defence to wear. The green dragonhide body requires the completion of Dragon Slayer quest to wield. The green dragonhide coif may be purchased at the grand exchange or at Fist of Guthix with tokens obtained from the minigame.
Magic armor is the weakest armor in the game. It barely has any defence bonuses and it requires low levels to wear. For starters, there is the blue wizard set. It does not have any requirements and it is easy to obtain. For stronger mages, there is the combat and druidic robes. These are the best f2p robes but they are expensive if not obtained at fist of guthix. Most mages will also have melee shields or anti-dragon shield with them for added protection.