Orders placed by users are divided into Taker and Maker transactions.
A Taker order is a placed order executed instantly by a response order in the order book. Thus, Taker transaction spends liquidity by taking an order from the list. If you place a market order or use the Quick Exchange option, such transaction is always considered a Taker order.
A Maker order is a placed order that is not bought out immediately but remains in the list of orders to be executed in the future instead. Limit and stop orders can be either a Taker or a Maker transaction depending on whether this order is part of the order book (if it took part in its formation, then it is considered a Maker order) or it has executed an order that was already in the order book” (then it is considered a Taker order).
Maker transactions provide liquidity, while Taker transactions lower liquidity.