Maker refers to a trader place an order above the current ticker price for selling or below the current ticker price for buying. Makers add liquidity to the market and there’s a maker fee charged.
Taker refers to the trader’s initiative to fill a certain number of orders at the current market price and immediately close the existing orders. And a taker fee is, therefore, be generated.
Meanwhile, when a trader’s order doesn’t fill immediately, under the case of a limit order, for example, the trader becomes a maker.