Minecraft Economy Servers
Economy servers add an extra dimension to normal Minecraft gameplay by operating a virtual economy within the server. The key feature found on all economy servers is an in-game currency that players can earn, save and spend. Most aspects of gameplay and other features on the server are linked to this currency.
One very common feature is a marketplace system, which allows players to create custom shops and earn money by selling resources. More advanced features include an auction house for buying and selling rare or unique items, banks where players can deposit money and earn interest, and a jobs system where players can choose a profession and work for a salary.
Overall, economy servers are usually highly competitive, and are perfect if you want to add some extra complexity to regular survival Minecraft.