When placing a trade on the exchange, the trading fees you will pay depend on whether you are considered a Maker or a Taker.
You are a Taker if you place an order at the market price (typically a “market” order) and it is immediately matched against another customers order on the order book. As a Taker you will incur a trading fee, please see our fees section here.
You are a Maker if you place an order (typically a “limit” order) and it is not immediately matched against an existing order on the order book.
If you are a Maker and another customer places an order that matches your own, you will incur a 0% fee on that trade, as you are adding liquidity to the books.
In general Maker/Taker fees are considered to be beneficial to maintaining a healthy and liquid market.