API GetAuctionItemClasses

Gets a list of the auction house item classes. class1, class2, class3, ... = GetAuctionItemClasses

Returns

 * class1, class2, class3, ... : String - localized item class.

Example
local itemClasses = { GetAuctionItemClasses }; if #itemClasses > 0 then local itemClass; for _, itemClass in pairs(itemClasses) do    DEFAULT_CHAT_FRAME:AddMessage(itemClass); end end

Result

This will give you the names of every category, in the client's language. As of 4.0.6 on an English client, the results are:
 * "Weapon"
 * "Armor"
 * "Container"
 * "Consumable"
 * "Glyph"
 * "Trade Goods"
 * "Recipe"
 * "Gem"
 * "Miscallaneous"
 * "Quest"