Money
One of the in game currencies that the FruitySMP uses is Money.
At any time, you can either use /balance or look on the Money Section on your scoreboard to view how much money you have.
You can use this money to purchase things on the auction house, /pay people, purchase items off of /shop, and more.
There are many ways to obtain money on the FruitySMP. The main ones being selling items on the auction house or to the server, creating chestshops, etc.
A good way to make money on the server is to sell cookies. You can do this by making them and using /sell cookie. Cookies go for $4 each and are a great way of making some quick and easy money.
Selling cookies aren't the only items you can sell though. There are lots of things that you can sell to the server for some cash. You can use /worth (item) to see how much a certain item sells to the server for.
If you have a valuable item or some other stuff that doesn't sell to the server, then you can use the auction house. This is where players can sell their items to other players for money.
To sell on the auction house, hold the item you wish to sell and run the command /ah sell (price) to list that item.