This page contains high level (user level) description of items.
That are items, info about stats, sockets. More in-depth description (containing algorithms and implementation details) can be found here

Item can be obtained as a drop from a monster, from opening box / looting, or by interacting with NPCs (buying item from store).
Some items can be equipped (such as swords, armor, orbs), and they usually have preffered equipment slot.
That means, that sword might be equipped to left / right hand only.
On the other hand, platelegs must be equipped to legs equipment slot, and so on...

Non equipable items can be used for crafting or in quests.

Each item has some size. That includes \(itemWidth\) and \(itemHeight\).
The size is defined for each item and does not change.
Minimum size of item is \(1 * 1 = 1\) square, maximum size is \(4 * 4 = 16\) squares
The bigger the item, the more space is required in inventory to place it there.

Upon drop, basic statistics for the item are generated.
So if you get 2 same items (for example steel sword) as a drop, they both can (and probably will) have different stats, and different amount of sockets

Item might have some number of sockets, that is never greater than \(itemWidth * itemHeight\), hoever, an item without any sockets can exist.
Upon drop, the number of sockets is generated for that item.

Socket can be used to insert any gem (if user meets the requirements to do so), which usually modifies the item stats.
Therefore, the more sockets item has, the more powerful it can potentially be, and the more valuable is.

Gems and potions do not have any sockets.