There are 12 Item Types in 4 Categories (Common, Uncommon, Rare & Epic)

Basic Tools
Used for some economic, building and siege weapon Techs and Cards
Scroll of Knowledge
Used for some research and building Techs and Cards
Blueprint
Used for most building Techs and Cards
Gemstone
Used for many general Techs and Cards
Practice Weapons
Used for some military unit and battle Techs and Cards

Fine Ale
Used for Dwarven and Hero unit Techs and Cards
Advanced Tools
Used for many building and siege weapon Techs and Cards
Relic
Used for magic, spells and elven building Techs and Cards

Legendary Weapons
Used for hero and advanced military Techs and Cards
Legendary Banner
Used for mounted units and some economy Techs and Cards

Monster Snare
Used for dragon, hydra and other monster Techs and Cards
Tome of Magic
Used for wizard, magic and spell Techs and Cards

When you receive a reward, the game will be told how many different types of items you will be given, usually based on Difficulty or some other factor.

The types of items you are given are determined by first randomly picking a category, with the following chances (in most cases):
Common = 50%
Uncommon = 25%
Rare = 15%
Epic = 10%

And then you are given item you have the least of within that category or randomly chooses between those items you have least of if there is more than one.

Once the specific item is chosen, the quantity varies by category, that is:
Common = 4 items
Uncommon = 3 items
Rare = 2 items
Epic = 1 item

Each day you log in you will get a Crafting reward of one Item Type. If you belong to a Guild, you will get an additional Item Type or double of the one Item type.

In online SP and MP battles, if you lose your Town Flag you will receive Common category items as your defeat reward. For unrated/challenge/custom battles the reward is one Item Type, for rated battles you get one for 1vs1, two for 2vs2 and three for FFA.

In online SP and MP battles, when you capture the Town Flag of an enemy, you will receive a number of Item Types based on the Difficulty level of your opponent - one for Easy AI, two for Medium AI and three for Hard AI or Human Players.

In online SP and MP battles, when your Team is the last one left standing, each team member that is still playing the map will receive a Team Victory reward. For unrated/challenge/custom battles the reward is two Item Types, for rated battles you get two for 1vs1, three for 2vs2 and four for FFA.

In the Campaign, if you are not Offline, you will be given rewards at various checkpoints and on completion of each Chapter. The number of Item Types given depends on the difficuly level.

In the Zombie Survival mode, both singleplayer and CoOp, you will be given increasingly better rewards for every three waves survived. The number of Item Types given depends on the difficuly level.

In online SP and MP battles with Dragon Treasure turned on, and in some Campaign chapters, there is a Treasure Chest somewhere on the map that can only be collected by Hero or Wizard units. The Treasure Chests are often guarded by a Dragon that has to be defeated before the chest can be opened and so give higher category rewards (equal chance of Uncommon, Rare and Epic).

Crafting Items can be traded with other players via the Trade window. You can place an Offer for an Item Type/Amount you want to trade and what Item Type/Amount you want in return for it and you can browse and accept Offers from other players.

You can give items to any player who is Online, via the Social window's Friends and Online tabs or the Guild window using the Send Items button. This is useful when you have a friend start playing the game and you want get them started with Crafting.