On this page of the Diablo 2 Resurrected guide, you'll learn how to repair broken weaponry or other items. Your equipment gets damaged overtime. This applies both to weapons and armor. When an equipped item breaks completely, it's no longer able to fulfill its offensive / defensive purpose and doesn't provide any bonuses. Fortunately you don't have to worry about it too much -a pop-up about your equipment's condition deteriorating will appear on the right side of the screen, long before the item actually breaks.
How to repair my inventory items?
Repair doesn't cost much and it's not necessary too often. Your items can be repaired by any blacksmith in the Act's respective town / camp. In Act 1 said blacksmith is Charsi.
Once the trading screen opens, you'll see an anvil icon in the lower right corner - by clicking it you'll repair all of your equipment. This also replenishes all ammo in thrown weapons, such as javelins or throwing knives. This does not apply to bows, crossbows or grenades.
Which items cannot be repaired?
The only exception to the aforementioned rules are ethereal items. These cannot be repaired. Ethereal items will last you longer if you avoid melee combat. Once an ethereal item breaks, it's gone forever.