World of Warcraft starts all new characters with a tiny bit of equipment, which generally means you'll start out with a shirt and a weapon of some type, but ZERO cash to buy new things.
If you're like me, you'll jump on the quests because it's the best way to advance at this level, without regular boring grinding of whatever monsters you find running around.
As you progress through the quests, it's likely you're going to die a few times while you figure out how everything works, how close you can get to aggressives and exactly how many mobs you can take on, successfully, at one time.
Death's Durability Detriment
Every time you die, your equipped items degrade in quality by 10% of their full quality. This means that after 10 deaths, your equipment will be at 0 durability and won't be usable anymore.
The first time I saw the full impact of this durability thing was after I had died a number of times - one time when I went to attack a Boar of some sort in Durotar, I didn't attack with my weapon and instead was PUNCHING my opponent! Sure, my unarmed combat skill was improving with every punch, but what happened to my weapon??
After finishing the boar off, I looked in my 'c' Combat screen and saw that my weapon was still in the main hand slot, so I hovered my mouse over it and noticed the durability was at zero. I had fought my weapon down to a nub!
Visit Armorers and Weaponists
I really don't recall how I figured it out - maybe I looked it up on the World of Warcraft website, maybe I merely used Google - but it's the various Shopkeeps that can repair your equipment while also selling you new stuff.
Only certain types of shopkeeps can repair your equipment, but really, it makes sense when you look at their job descriptions. The Bread Vendor in Thunder Bluff, for example, cannot repair your equipment. Neither can the Fishing Supplies civilian. But, the Light Armor Merchant and the Weaponsmith and those types of civilians can help you out.
By default, the "repair" button at the bottom of the shopkeep window only repairs equipped items and doesn't repair those in your bags that also need repair (for example, if you let the Spirit Healer bring you back to life, your equipped AND inventory items lose 25% durability), but one of the WoW UI Mods I have in place is Always Repair All that I found on Curse Gaming's website. If you install this Interface Addon, it changes that repair option so it repairs all in your inventory as well as your equipped items.
Other Affects of Reduced Durability
From what I can see, there are no other adverse affects to having the durability of your equipment reduced. I have not seen that the armor or weapon class ratings have dwindled with the lower quality, but I could be wrong, so watch out.
I make it a regular habit to visit someone who can repair my equipment every time I visit a town. Normally it's easy to do because I'm visiting those shopkeeps anyway, for selling and buying purposes. You can easily make it a regular part of your adventuring days, knowing the information!