A Maker (maker order) adds liquidity to an order book by placing orders that are not instantly filled.
Maker orders sit in the NBX order book until another order (called a taker order) that matches its criteria is placed. This “taker” order is then matched with the corresponding maker order. One example of a maker order is a limit order, which waits to be filled until the asset involved reaches a certain price in a set timeframe. If the timeframe expires and the asset never reaches the limit order’s price, then the order expires.
As suggested above, a Taker (taker order) removes liquidity from the order book by creating orders that are instantly matched against existing orders (maker orders) in the orderbook. A market order is the key example of a taker order, because it always removes liquidity by instantly matching with existing orders (maker orders) in the order book.
See the Maker and Taker order fees here.