Guild Wars 2

I don’t fully understand when to buy those chests. What are the differences? I usually just buy the Gold ones because I was told the loot is worth it more than the Copper Silver chests. So what are their purpose?

copper, silver, & gold chest each have different drop rate for different sets of gear for their respected ranks.

If you just want to salvage stuff for dust/mats then copper chest is as good as gold.