Weapons and Armors in FOnline2 aren't indestructible like they used to be in Fallout series. Each time you use a weapon its get a little destroyed, each time you sustain damage your armor wear up. (Some meele weapons are exception to that rule.)
To cancel negative impact of time on item, a player with right amount of skillpoints invested in repair can attempt to fix damaged stuff. The more point you invest in repair, the better as you will have bigger chance to sukcesfully repair item.
Armors and Weapons have two values on them. Detoration means how much item is damaged right now. The futher it goes the bigger are damage. Durabillity means how much more item can be repaired. When the item detoration go to 100% but there is still some durabillity left item gains: "Small Defect" status which means that is unusable untill someone repair it. When item detoration reach 100% and there is no more durabillity on it items gains "Beyond repair" status and is as good as junk.
How to Repair
When to repair?
Each 10% points of detoration on armors means that some of defensive values of armor is lost.
In case of weapon no amount of detoration except for 100% will cause any trouble so repair weapons only if you thing that they might go to the max detoration soon.